CHAPTER 5
CHIMNEYS AND VENTS
SECTION 501 (IFGC)
GENERAL
501.1 Scope. This chapter shall govern the installation, maintenance, repair and approval of factory-built chimneys, chimney
liners, vents and connectors and the utilization of masonry
chimneys serving gas-fired appliances. The requirements for
the installation, maintenance, repair and approval of factory-built chimneys, chimney liners, vents and connectors
serving appliances burning fuels other than fuel gas shall be
regulated by the International Mechanical Code. The construction, repair, maintenance and approval of masonry chimneys
shall be regulated by the International Building Code.
501.2 General. Every appliance shall discharge the products of
combustion to the outdoors, except for appliances exempted by
Section 501.8.
501.3 Masonry chimneys. Masonry chimneys shall be constructed in accordance with Section 503.5.3 and the International Building Code.
501.4 Minimum size of chimney or vent. Chimneys and vents
shall be sized in accordance with Section 504.
501.5 Abandoned inlet openings. Abandoned inlet openings
in chimneys and vents shall be closed by an approved method.
501.6 Positive pressure. Where an appliance equipped with a
mechanical forced draft system creates a positive pressure in
the venting system, the venting system shall be designed for
positive pressure applications.
501.7 Connection to fireplace. Connection of appliances to
chimney flues serving fireplaces shall be in accordance with
Sections 501.7.1 through 501.7.3.
501.7.1 Closure and access. A noncombustible seal shall
be provided below the point of connection to prevent entry
of room air into the flue. Means shall be provided for access
to the flue for inspection and cleaning.
501.7.2 Connection to factory-built fireplace flue. An appliance shall not be connected to a flue serving a factory-built fireplace unless the appliance is specifically listed
for such installation. The connection shall be made in accordance with the appliance manufacturer’s installation instructions.
501.7.3 Connection to masonry fireplace flue. A connector shall extend from the appliance to the flue serving a masonry fireplace such that the flue gases are exhausted
directly into the flue. The connector shall be accessible or
removable for inspection and cleaning of both the connector
and the flue. Listed direct connection devices shall be installed in accordance with their listing.
501.8 Equipment not required to be vented. The following
appliances shall not be required to be vented.
1. Ranges.
2003 INTERNATIONAL FUEL GAS CODE®
2. Built-in domestic cooking units listed and marked for
optional venting.
3. Hot plates and laundry stoves.
4. Type 1 clothes dryers (Type 1 clothes dryers shall be exhausted in accordance with the requirements of Section
613).
5. A single booster-type automatic instantaneous water
heater, where designed and used solely for the sanitizing rinse requirements of a dishwashing machine, provided that the heater is installed in a commercial
kitchen having a mechanical exhaust system. Where installed in this manner, the draft hood, if required, shall
be in place and unaltered and the draft hood outlet shall
be not less than 36 inches (914 mm) vertically and 6
inches (152 mm) horizontally from any surface other
than the heater.
6. Refrigerators.
7. Counter appliances.
8. Room heaters listed for unvented use.
9. Direct-fired make-up air heaters.
10. Other equipment listed for unvented use and not provided with flue collars.
11. Specialized equipment of limited input such as laboratory burners and gas lights.
Where the appliances and equipment listed in Items 5
through 11 above are installed so that the aggregate input rating
exceeds 20 British thermal units (Btu) per hour per cubic feet
(207 watts per m3) of volume of the room or space in which
such appliances and equipment are installed, one or more shall
be provided with venting systems or other approved means for
conveying the vent gases to the outdoor atmosphere so that the
aggregate input rating of the remaining unvented appliances
and equipment does not exceed the 20 Btu per hour per cubic
foot (207 watts per m3) figure. Where the room or space in
which the equipment is installed is directly connected to another room or space by a doorway, archway, or other opening of
comparable size that cannot be closed, the volume of such adjacent room or space shall be permitted to be included in the calculations.
501.9 Chimney entrance. Connectors shall connect to a masonry chimney flue at a point not less than 12 inches (305 mm)
above the lowest portion of the interior of the chimney flue.
501.10 Connections to exhauster. Appliance connections to a
chimney or vent equipped with a power exhauster shall be
made on the inlet side of the exhauster. Joints on the positive
pressure side of the exhauster shall be sealed to prevent
flue-gas leakage as specified by the manufacturer’s installation
instructions for the exhauster.
501.11 Masonry chimneys. Masonry chimneys utilized to
vent appliances shall be located, constructed and sized as speci73
CHIMNEYS AND VENTS
fied in the manufacturer’s installation instructions for the appliances being vented and Section 503.
501.12 Residential and low-heat appliances flue lining systems. Flue lining systems for use with residential-type and
low-heat appliances shall be limited to the following:
1. Clay flue lining complying with the requirements of
ASTM C 315 or equivalent. Clay flue lining shall be installed in accordance with the International Building
Code.
2. Listed chimney lining systems complying with UL 1777.
3. Other approved materials that will resist, without cracking, softening or corrosion, flue gases and condensate at
temperatures up to 1,800°F (982°C).
501.13 Category I appliance flue lining systems. Flue lining
systems for use with Category I appliances shall be limited to
the following:
1. Flue lining systems complying with Section 501.12.
2. Chimney lining systems listed and labeled for use with
gas appliances with draft hoods and other Category I gas
appliances listed and labeled for use with Type B vents.
501.14 Category II, III and IV appliance venting systems.
The design, sizing and installation of vents for Category II, III
and IV appliances shall be in accordance with the appliance
manufacturer’s installation instructions.
501.15 Existing chimneys and vents. Where an appliance is
permanently disconnected from an existing chimney or vent, or
where an appliance is connected to an existing chimney or vent
during the process of a new installation, the chimney or vent
shall comply with Sections 501.15.1 through 501.15.4.
501.15.1 Size. The chimney or vent shall be resized as necessary to control flue gas condensation in the interior of the
chimney or vent and to provide the appliance or appliances
served with the required draft. For Category I appliances,
the resizing shall be in accordance with Section 502.
501.15.2 Flue passageways. The flue gas passageway shall
be free of obstructions and combustible deposits and shall
be cleaned if previously used for venting a solid or liquid
fuel-burning appliance or fireplace. The flue liner, chimney
inner wall or vent inner wall shall be continuous and shall be
free of cracks, gaps, perforations or other damage or deterioration which would allow the escape of combustion products, including gases, moisture and creosote.
501.15.3 Cleanout. Masonry chimney flues shall be provided with a cleanout opening having a minimum height of
6 inches (152 mm). The upper edge of the opening shall be
located not less than 6 inches (152 mm) below the lowest
chimney inlet opening. The cleanout shall be provided with
a tight-fitting, noncombustible cover.
501.15.4 Clearances. Chimneys and vents shall have airspace clearance to combustibles in accordance with the International Building Code and the chimney or vent
manufacturer’s installation instructions. Noncombustible
firestopping or fireblocking shall be provided in accordance
with the International Building Code.
Exception: Masonry chimneys equipped with a chimney lining system tested and listed for installation in
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chimneys in contact with combustibles in accordance
with UL 1777, and installed in accordance with the manufacturer’s instructions, shall not be required to have
clearance between combustible materials and exterior
surfaces of the masonry chimney.
SECTION 502 (IFGC)
VENTS
502.1 General. All vents, except as provided in Section 503.7,
shall be listed and labeled. Type B and BW vents shall be tested
in accordance with UL 441. Type L vents shall be tested in accordance with UL 641. Vents for Category II and III appliances
shall be tested in accordance with UL 1738. Plastic vents for
Category IV appliances shall not be required to be listed and labeled where such vents are as specified by the appliance manufacturer and are installed in accordance with the appliance
manufacturer’s installation instructions.
502.2 Connectors required. Connectors shall be used to connect appliances to the vertical chimney or vent, except where
the chimney or vent is attached directly to the appliance. Vent
connector size, material, construction and installation shall be
in accordance with Section 503.
502.3 Vent application. The application of vents shall be in accordance with Table 503.4.
502.4 Insulation shield. Where vents pass through insulated
assemblies, an insulation shield constructed of not less than 26
gage sheet (0.016 inch) (0.4 mm) metal shall be installed to provide clearance between the vent and the insulation material.
The clearance shall not be less than the clearance to combustibles specified by the vent manufacturer’s installation instructions. Where vents pass through attic space, the shield shall
terminate not less than 2 inches (51 mm) above the insulation
materials and shall be secured in place to prevent displacement.
Insulation shields provided as part of a listed vent system shall
be installed in accordance with the manufacturer’s installation
instructions.
502.5 Installation. Vent systems shall be sized, installed and
terminated in accordance with the vent and appliance manufacturer’s installation instructions and Section 503.
502.6 Support of vents. All portions of vents shall be adequately supported for the design and weight of the materials
employed.
SECTION 503 (IFGS)
VENTING OF EQUIPMENT
503.1 General. This section recognizes that the choice of venting materials and the methods of installation of venting systems
are dependent on the operating characteristics of the equipment
being vented. The operating characteristics of vented equipment can be categorized with respect to (1) positive or negative
pressure within the venting system; and (2) whether or not the
equipment generates flue or vent gases that might condense in
the venting system. See Section 202 for the definition of these
vented appliance categories.
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CHIMNEYS AND VENTS
503.2.1 Ventilating hoods. Ventilating hoods and exhaust
systems shall be permitted to be used to vent equipment installed in commercial applications (see Section 503.3.4) and
to vent industrial equipment, such as where the process itself
requires fume disposal.
503.2.2 Well-ventilated spaces. Where located in a large
and well-ventilated space, industrial equipment shall be permitted to be operated by discharging the flue gases directly
into the space.
503.2.3 Direct-vent equipment. Listed direct-vent equipment shall be considered properly vented where installed in
accordance with the terms of its listing, the manufacturer’s
instructions, and Section 503.8, Item 3.
503.2.4 Equipment with integral vents. Equipment incorporating integral venting means shall be considered properly vented when installed in accordance with its listing, the
manufacturer’s instructions, and Section 503.8, Items 1 and
2.
503.3 Design and construction. A venting system shall be designed and constructed so as to develop a positive flow adequate to convey flue or vent gases to the outdoor atmosphere.
503.3.1 Equipment draft requirements. A venting system
shall satisfy the draft requirements of the equipment in accordance with the manufacturer’s instructions.
503.3.2 Design and construction. Gas utilization equipment required to be vented shall be connected to a venting
system designed and installed in accordance with the provisions of Sections 503.4 through 503.15.
503.3.3 Mechanical draft systems. Mechanical draft systems shall comply with the following:
1. Mechanical draft systems shall be listed and shall be
installed in accordance with the terms of their listing
and both the appliance and the mechanical draft system manufacturer’s instructions.
2. Equipment, except incinerators, requiring venting
shall be permitted to be vented by means of mechanical draft systems of either forced or induced draft design.
3. Forced draft systems and all portions of induced draft
systems under positive pressure during operation
shall be designed and installed so as to prevent leakage of flue or vent gases into a building.
4. Vent connectors serving equipment vented by natural
draft shall not be connected into any portion of mechanical draft systems operating under positive pressure.
5. When a mechanical draft system is employed, provision shall be made to prevent the flow of gas to the
main burners when the draft system is not performing
so as to satisfy the operating requirements of the
equipment for safe performance.
2003 INTERNATIONAL FUEL GAS CODE®
6. The exit terminals of mechanical draft systems shall
be not less than 7 feet (2134 mm) above grade where
located adjacent to public walkways and shall be located as specified in Section 503.8, Items 1 and 2.
503.3.4 Ventilating hoods and exhaust systems. Ventilating hoods and exhaust systems shall be permitted to be
used to vent gas utilization equipment installed in commercial applications. Where automatically operated equipment
is vented through a ventilating hood or exhaust system
equipped with a damper or with a power means of exhaust,
provisions shall be made to allow the flow of gas to the main
burners only when the damper is open to a position to properly vent the equipment and when the power means of exhaust is in operation.
503.3.5 Circulating air ducts and furnace plenums. No
portion of a venting system shall extend into or pass through
any circulating air duct or furnace plenum.
503.4 Type of venting system to be used. The type of venting
system to be used shall be in accordance with Table 503.4.
503.4.1 Plastic piping. Plastic piping used for venting
equipment listed for use with such venting materials shall be
approved.
503.4.2 Special gas vent. Special gas vent shall be listed
and installed in accordance with the terms of the special gas
vent listing and the manufacturers’ instructions.
503.5 Masonry, metal, and factory-built chimneys. Masonry, metal and factory-built chimneys shall comply with Sections 503.5.1 through 503.5.10.
503.5.1 Factory-built chimneys. Factory-built chimneys
shall be installed in accordance with their listing and the
manufacturers’ instructions. Factory-built chimneys used to
vent appliances that operate at positive vent pressure shall
be listed for such application.
503.5.2 Metal chimneys. Metal chimneys shall be built and
installed in accordance with NFPA 211.
503.5.3 Masonry chimneys. Masonry chimneys shall be
built and installed in accordance with NFPA 211 and shall
be lined with approved clay flue lining, a listed chimney lining system, or other approved material that will resist corrosion, erosion, softening, or cracking from vent gases at
temperatures up to 1800°F (982°C).
Exception: Masonry chimney flues serving listed gas
appliances with draft hoods, Category I appliances, and
other gas appliances listed for use with Type B vent shall
be permitted to be lined with a chimney lining system
specifically listed for use only with such appliances. The
liner shall be installed in accordance with the liner manufacturer’s instructions and the terms of the listing. A permanent identifying label shall be attached at the point
where the connection is to be made to the liner. The label
shall read: “This chimney liner is for appliances that burn
gas only. Do not connect to solid or liquid fuel-burning
appliances or incinerators.”
For information on installation of gas vents in existing
masonry chimneys, see Section 503.6.5.
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503.2 Venting systems required. Except as permitted in Sections 503.2.1 through 503.2.4 and 501.8, all equipment shall be
connected to venting systems.
CHIMNEYS AND VENTS
TABLE 503.4
TYPE OF VENTING SYSTEM TO BE USED
GAS UTILIZATION EQUIPMENT
TYPE OF VENTING SYSTEM
Listed Category I equipment
Listed equipment equipped with draft hood
Equipment listed for use with Type B gas vent
Type B gas vent (Section 503.6)
Chimney (Section 503.5)
Single-wall metal pipe (Section 503.7)
Listed chimney lining system for gas venting (Section 503.5.3)
Special gas vent listed for this equipment (Section 503.4.2)
Listed vented wall furnaces
Type B-W gas vent (Sections 503.6, 607)
Category II equipment
As specified or furnished by manufacturers of listed equipment
(Sections 503.4.1, 503.4.2)
Category III equipment
As specified or furnished by manufacturers of listed equipment
(Sections 503.4.1, 503.4.2)
Category IV equipment
As specified or furnished by manufacturers of listed equipment
(Sections 503.4.1, 503.4.2)
Incinerators, indoors
Chimney (Section 503.5)
Incinerators, outdoors
Single-wall metal pipe (Sections 503.7, 503.7.6)
Equipment which may be converted to use of solid fuel
Chimney (Section 503.5)
Unlisted combination gas and oil-burning equipment
Chimney (Section 503.5)
Listed combination gas and oil-burning equipment
Type L vent (Section 503.6) or chimney (Section 503.5)
Combination gas and solid fuel-burning equipment
Chimney (Section 503.5)
Equipment listed for use with chimneys only
Chimney (Section 503.5)
Unlisted equipment
Chimney (Section 503.5)
Decorative appliance in vented fireplace
Chimney
Gas-fired toilets
Single-wall metal pipe (Section 625)
Direct vent equipment
See Section 503.2.3
Equipment with integral vent
See Section 503.2.4
503.5.4 Chimney termination. Chimneys for residential-type or low-heat gas utilization equipment shall extend at
least 3 feet (914 mm) above the highest point where it passes
through a roof of a building and at least 2 feet (610 mm)
higher than any portion of a building within a horizontal distance of 10 feet (3048 mm) (see Figure 503.5.4). Chimneys
for medium-heat equipment shall extend at least 10 feet
(3048 mm) higher than any portion of any building within 25
feet (7620 mm). Chimneys shall extend at least 5 feet (1524
mm) above the highest connected equipment draft hood outlet or flue collar. Decorative shrouds shall not be installed at
the termination of factory-built chimneys except where such
shrouds are listed and labeled for use with the specific factory-built chimney system and are installed in accordance
with the manufacturers’ installation instructions.
503.5.5 Size of chimneys. The effective area of a chimney
venting system serving listed appliances with draft hoods,
Category I appliances, and other appliances listed for use
with Type B vents shall be determined in accordance with
one of the following methods:
1. The provisions of Section 504.
2. For sizing an individual chimney venting system for a
single appliance with a draft hood, the effective areas
of the vent connector and chimney flue shall be not
76
less than the area of the appliance flue collar or draft
hood outlet, nor greater than seven times the draft
hood outlet area.
3. For sizing a chimney venting system connected to two
appliances with draft hoods, the effective area of the
chimney flue shall be not less than the area of the
larger draft hood outlet plus 50 percent of the area of
the smaller draft hood outlet, nor greater than seven
times the smallest draft hood outlet area.
4. Chimney venting systems using mechanical draft
shall be sized in accordance with approved engineering methods.
5. Other approved engineering methods.
503.5.5.1 Incinerator venting. Where an incinerator is
vented by a chimney serving other gas utilization equipment, the gas input to the incinerator shall not be included in calculating chimney size, provided the
chimney flue diameter is not less than 1 inch (25 mm)
larger in equivalent diameter than the diameter of the incinerator flue outlet.
503.5.6 Inspection of chimneys. Before replacing an existing appliance or connecting a vent connector to a chimney,
the chimney passageway shall be examined to ascertain that
2003 INTERNATIONAL FUEL GAS CODE®
CHIMNEYS AND VENTS
it is clear and free of obstructions and it shall be cleaned if
previously used for venting solid or liquid fuel-burning appliances or fireplaces.
503.5.6.1 Chimney lining. Chimneys shall be lined in
accordance with NFPA 211.
Exception: Existing chimneys shall be permitted to
have their use continued when an appliance is replaced by an appliance of similar type, input rating,
and efficiency.
503.5.6.2 Cleanouts. Cleanouts shall be examined to determine if they will remain tightly closed when not in use.
503.5.6.3 Unsafe chimneys. Where inspection reveals
that an existing chimney is not safe for the intended application, it shall be repaired, rebuilt, lined, relined, or replaced with a vent or chimney to conform to NFPA 211
and it shall be suitable for the equipment to be vented.
503.5.7 Chimneys serving equipment burning other fuels. Chimneys serving equipment burning other fuels shall
comply with Sections 503.5.7.1 through 503.5.7.4.
503.5.7.1 Solid fuel-burning appliances. Gas utilization equipment shall not be connected to a chimney flue
serving a separate appliance designed to burn solid fuel.
503.5.7.2 Liquid fuel-burning appliances. Where one
chimney flue serves gas utilization equipment and equipment burning liquid fuel, the equipment shall be connected through separate openings or shall be connected
through a single opening where joined by a suitable fitting located as close as practical to the chimney. Where
two or more openings are provided into one chimney
flue, they shall be at different levels. Where the gas utilization equipment is automatically controlled, it shall be
equipped with a safety shutoff device.
503.5.7.3 Combination gas and solid fuel-burning appliances. A combination gas- and solid fuel-burning appliance shall be permitted to be connected to a single
chimney flue where equipped with a manual reset device
to shut off gas to the main burner in the event of sustained
backdraft or flue gas spillage. The chimney flue shall be
sized to properly vent the appliance.
503.5.7.4 Combination gas- and oil fuel-burning appliances. A listed combination gas- and oil fuel-burning
appliance shall be permitted to be connected to a single
chimney flue. The chimney flue shall be sized to properly
vent the appliance.
503.5.8 Support of chimneys. All portions of chimneys
shall be supported for the design and weight of the materials
employed. Factory-built chimneys shall be supported and
spaced in accordance with their listings and the manufacturer’s instructions.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
FIGURE 503.5.4
TYPICAL TERMINATION LOCATIONS FOR
CHIMNEYS AND SINGLE-WALL METAL PIPES SERVING
RESIDENTIAL-TYPE AND LOW-HEAT EQUIPMENT
2003 INTERNATIONAL FUEL GAS CODE®
503.5.9 Cleanouts. Where a chimney that formerly carried
flue products from liquid or solid fuel-burning appliances is
used with an appliance using fuel gas, an accessible
cleanout shall be provided. The cleanout shall have a
tight-fitting cover and shall be installed so its upper edge is
at least 6 inches (152 mm) below the lower edge of the lowest chimney inlet opening.
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CHIMNEYS AND VENTS
503.5.10 Space surrounding lining or vent. The remaining space surrounding a chimney liner, gas vent, special gas
vent, or plastic piping installed within a masonry chimney
flue shall not be used to vent another appliance. The insertion of another liner or vent within the chimney as provided
in this code and the liner or vent manufacturer’s instructions
shall not be prohibited.
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The remaining space surrounding a chimney liner, gas
vent, special gas vent, or plastic piping installed within a
masonry, metal or factory-built chimney, shall not be used to
supply combustion air. Such space shall not be prohibited
from supplying combustion air to direct-vent appliances designed for installation in a solid fuel-burning fireplace and
installed in accordance with the listing and the manufacturer’s instructions.
503.6 Gas vents. Gas vents shall comply with Sections 503.6.1
through 503.6.12 (see Section 202, Definitions).
2.
3.
4.
5.
6.
nated in accordance with Figure 503.6.6, provided
that such vents are at least 8 feet (2438 mm) from a
vertical wall or similar obstruction. All other gas vents
shall terminate not less than 2 feet (610 mm) above the
highest point where they pass through the roof and at
least 2 feet (610 mm) higher than any portion of a
building within 10 feet (3048 mm).
As provided for industrial equipment in Section
503.2.2.
As provided for direct-vent systems in Section
503.2.3.
As provided for equipment with integral vents in Section 503.2.4.
As provided for mechanical draft systems in Section
503.3.3.
As provided for ventilating hoods and exhaust systems in Section 503.3.4.
503.6.1 Installation, general. Gas vents shall be installed
in accordance with the terms of their listings and the manufacturer’s instructions.
503.6.2 Type B-W vent capacity. A Type B-W gas vent
shall have a listed capacity not less than that of the listed
vented wall furnace to which it is connected.
503.6.3 Roof penetration. A gas vent passing through a
roof shall extend through the roof flashing, roof jack, or roof
thimble and shall be terminated by a listed termination cap.
503.6.4 Offsets. Type B and Type L vents shall extend in a
generally vertical direction with offsets not exceeding 45
degrees (0.79 rad), except that a vent system having not
more than one 60-degree (1.04 rad) offset shall be permitted. Any angle greater than 45 degrees (0.79 rad) from the
vertical is considered horizontal. The total horizontal length
of a vent plus the horizontal vent connector length serving
draft-hood-equipped appliances shall not be greater than 75
percent of the vertical height of the vent.
Exception: Systems designed and sized as provided in
Section 504 or in accordance with other approved engineering methods.
Vents serving Category I fan-assisted appliances shall be
installed in accordance with the appliance manufacturer’s
instructions and Section 504 or other approved engineering
methods.
503.6.5 Gas vents installed within masonry chimneys. Gas
vents installed within masonry chimneys shall be installed in
accordance with the terms of their listing and the manufacturer’s installation instructions. Gas vents installed within
masonry chimneys shall be identified with a permanent label
installed at the point where the vent enters the chimney. The
label shall contain the following language: “This gas vent is
for appliances that burn gas. Do not connect to solid or liquid
fuel-burning appliances or incinerators.”
503.6.6 Gas vent terminations. A gas vent shall terminate
in accordance with one of the following:
1. Above the roof surface with a listed cap or listed roof
assembly. Gas vents 12 inches (305 mm) in size or
smaller with listed caps shall be permitted to be termi78
ROOF PITCH
H (min) ft
Flat to 6/12
1.0
Over 6/12 to 7/12
1.25
Over 7/12 to 8/12
1.5
Over 8/12 to 9/12
2.0
Over 9/12 to 10/12
2.5
Over 10/12 to 11/12
3.25
Over 11/12 to 12/12
4.0
Over 12/12 to 14/12
5.0
Over 14/12 to 16/12
6.0
Over 16/12 to 18/12
7.0
Over 18/12 to 20/12
7.5
Over 20/12 to 21/12
8.0
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
FIGURE 503.6.6
GAS VENT TERMINATION LOCATIONS FOR
LISTED CAPS 12 INCHES OR LESS IN SIZE AT
LEAST 8 FEET FROM A VERTICAL WALL
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CHIMNEYS AND VENTS
503.6.6.1 Decorative shrouds. Decorative shrouds shall
not be installed at the termination of gas vents except
where such shrouds are listed for use with the specific gas
venting system and are installed in accordance with manufacturer’s installation instructions.
503.6.7 Minimum height. A Type B or a Type L gas vent
shall terminate at least 5 feet (1524 mm) in vertical height
above the highest connected equipment draft hood or flue
collar. A Type B-W gas vent shall terminate at least 12 feet
(3658 mm) in vertical height above the bottom of the wall
furnace.
503.6.8 Exterior wall penetrations. A gas vent extending
through an exterior wall shall not terminate adjacent to the
wall or below eaves or parapets, except as provided in Sections 503.2.3 and 503.3.3.
503.6.9 Size of gas vents. Venting systems shall be sized
and constructed in accordance with Section 504 or other approved engineering methods and the gas vent and gas equipment manufacturers’ instructions.
503.6.9.1 Category I appliances. The sizing of natural
draft venting systems serving one or more listed appliances equipped with a draft hood or appliances listed for
use with Type B gas vent, installed in a single story of a
building, shall be in accordance with one of the following
methods:
Exceptions:
1. The provisions of Section 504.
2. For sizing an individual gas vent for a single,
draft-hood-equipped appliance, the effective
area of the vent connector and the gas vent shall
be not less than the area of the appliance draft
hood outlet, nor greater than seven times the
draft hood outlet area.
arated from habitable space. Each of these rooms shall
have provisions for an adequate supply of combustion,
ventilation, and dilution air that is not supplied from habitable space (see Figure 503.6.10.1).
503.6.10.2 Sizing. The size of the connectors and common segments of multistory venting systems for equipment listed for use with Type B double-wall gas vent
shall be in accordance with Table 504.3(1) and Figures
B-13 and B-14 in Appendix B, provided:
1. The available total height (H) for each segment of a
multistory venting system is the vertical distance
between the level of the highest draft hood outlet or
flue collar on that floor and the centerline of the
next highest interconnection tee (see Figure B-13).
2. The size of the connector for a segment is determined from its gas utilization equipment heat input
and available connector rise, and shall not be
smaller than the draft hood outlet or flue collar
size.
3. The size of the common vertical segment, and of
the interconnection tee at the base of that segment,
shall be based on the total gas utilization equipment heat input entering that segment and its available total height.
503.6.11 Support of gas vents. Gas vents shall be supported and spaced in accordance with their listings and the
manufacturer’s instructions.
503.6.12 Marking. In those localities where solid and liquid fuels are used extensively, gas vents shall be permanently identified by a label attached to the wall or ceiling at a
point where the vent connector enters the gas vent. The de-
3. For sizing a gas vent connected to two appliances with draft hoods, the effective area of the
vent shall be not less than the area of the larger
draft hood outlet plus 50 percent of the area of
the smaller draft hood outlet, nor greater than
seven times the smaller draft hood outlet area.
4. Approved engineering practices.
503.6.9.2 Category II, III, and IV appliances. The sizing of gas vents for Category II, III, and IV equipment
shall be in accordance with the equipment manufacturer’s instructions.
503.6.9.3 Mechanical draft. Chimney venting systems
using mechanical draft shall be sized in accordance with
approved engineering methods.
503.6.10 Gas vents serving equipment on more than one
floor. A single or common gas vent shall be permitted in
multistory installations to vent Category I equipment located on more than one floor level, provided the venting system is designed and installed in accordance with this section
and approved engineering methods.
503.6.10.1 Equipment separation. All equipment connected to the common vent shall be located in rooms sep2003 INTERNATIONAL FUEL GAS CODE®
FIGURE 503.6.10.1
PLAN VIEW OF PRACTICAL SEPARATION METHOD
FOR MULTISTORY GAS VENTING
79
CHIMNEYS AND VENTS
termination of where such localities exist shall be made by
the code official. The label shall read:
“This gas vent is for appliances that burn gas. Do not connect to solid or liquid fuel-burning appliances or incinerators.”
503.7 Single-wall metal pipe. Single-wall metal pipe vents
shall comply with Sections 503.7.1 through 503.7.12.
503.7.1 Construction. Single-wall metal pipe shall be constructed of galvanized sheet steel not less than 0.0304 inch
(0.7 mm) thick, or other approved, noncombustible, corrosion-resistant material.
503.7.2 Cold climate. Uninsulated single-wall metal pipe
shall not be used outdoors in cold climates for venting gas
utilization equipment.
503.7.3 Termination. Single-wall metal pipe shall terminate at least 5 feet (1524 mm) in vertical height above the
highest connected equipment draft hood outlet or flue collar. Single-wall metal pipe shall extend at least 2 feet (610
mm) above the highest point where it passes through a roof
of a building and at least 2 feet (610 mm) higher than any
portion of a building within a horizontal distance of 10 feet
(3048 mm) (see Figure 503.5.4). An approved cap or roof
assembly shall be attached to the terminus of a single-wall
metal pipe (see also Section 503.7.8, Item 3).
top. The thimble shall be sized in accordance with Section
503.10.16.
503.7.6 Installation. Single-wall metal pipe shall not originate in any unoccupied attic or concealed space and shall not
pass through any attic, inside wall, concealed space, or floor.
The installation of a single-wall metal pipe through an exterior combustible wall shall comply with Section 503.10.15.
Single-wall metal pipe used for venting an incinerator shall
be exposed and readily examinable for its full length and
shall have suitable clearances maintained.
503.7.7 Clearances. Minimum clearances from single-wall
metal pipe to combustible material shall be in accordance
with Table 503.7.7. The clearance from single-wall metal
pipe to combustible material shall be permitted to be reduced where the combustible material is protected as specified for vent connectors in Table 308.2.
503.7.8 Size of single-wall metal pipe. A venting system
constructed of single-wall metal pipe shall be sized in accordance with one of the following methods and the equipment
manufacturer’s instructions:
1. For a draft-hood-equipped appliance, in accordance
with Section 504.
2. For a venting system for a single appliance with a draft
hood, the areas of the connector and the pipe each
shall be not less than the area of the appliance flue collar or draft hood outlet, whichever is smaller. The vent
area shall not be greater than seven times the draft
hood outlet area.
503.7.4 Limitations of use. Single-wall metal pipe shall be
used only for runs directly from the space in which the
equipment is located through the roof or exterior wall to the
outdoor atmosphere.
503.7.5 Roof penetrations. A pipe passing through a roof
shall extend without interruption through the roof flashing,
roof jacket, or roof thimble. Where a single-wall metal pipe
passes through a roof constructed of combustible material, a
noncombustible, nonventilating thimble shall be used at the
point of passage. The thimble shall extend at least 18 inches
(457 mm) above and 6 inches (152 mm) below the roof with
the annular space open at the bottom and closed only at the
3. Other approved engineering methods.
503.7.9 Pipe geometry. Any shaped single-wall metal pipe
shall be permitted to be used, provided that its equivalent effective area is equal to the effective area of the round pipe for
which it is substituted, and provided that the minimum internal dimension of the pipe is not less than 2 inches (51 mm).
TABLE 503.7.7a
CLEARANCES FOR CONNECTORS
MINIMUM DISTANCE FROM COMBUSTIBLE MATERIAL
Listed Type B gas
vent material
Listed Type L
vent material
Single-wall
metal pipe
Factory-built
chimney sections
Listed equipment with draft hoods and equipment listed for
use with Type B gas vents
As listed
As listed
6 inches
As listed
Residential boilers and furnaces with listed gas conversion
burner and with draft hood
6 inches
6 inches
9 inches
As listed
Residential appliances listed for use with Type L vents
Not permitted
As listed
9 inches
As listed
Listed gas-fired toilets
Not permitted
As listed
As listed
As listed
Unlisted residential appliances with draft hood
Not permitted
6 inches
9 inches
As listed
Residential and low-heat equipment other than above
Not permitted
9 inches
18 inches
As listed
Medium-heat equipment
Not permitted
Not permitted
36 inches
As listed
EQUIPMENT
For SI: 1 inch = 25.4 mm.
a. These clearances shall apply unless the listing of an appliance or connector specifies different clearances, in which case the listed clearances shall apply.
80
2003 INTERNATIONAL FUEL GAS CODE®
CHIMNEYS AND VENTS
503.7.10 Termination capacity. The vent cap or a roof assembly shall have a venting capacity not less than that of the
pipe to which it is attached.
503.10 Vent connectors for Category I equipment. Vent connectors for Category I equipment shall comply with Sections
503.10.1 through 503.10.16.
503.7.11 Support of single-wall metal pipe. All portions
of single-wall metal pipe shall be supported for the design
and weight of the material employed.
503.10.1 Where required. A vent connector shall be used
to connect equipment to a gas vent, chimney, or single-wall
metal pipe, except where the gas vent, chimney, or single-wall metal pipe is directly connected to the equipment.
503.7.12 Marking. Single-wall metal pipe shall comply
with the marking provisions of Section 503.6.12.
503.8 Venting system termination location. The location of
venting system terminations shall comply with the following
(see Appendix C):
1. A mechanical draft venting system shall terminate at
least 3 feet (914 mm) above any forced-air inlet located
within 10 feet (3048 mm).
Exceptions:
1. This provision shall not apply to the combustion air intake of a direct-vent appliance.
2. This provision shall not apply to the separation
of the integral outdoor air inlet and flue gas discharge of listed outdoor appliances.
2. A mechanical draft venting system, excluding direct-vent appliances, shall terminate at least 4 feet (1219
mm) below, 4 feet (1219 mm) horizontally from, or 1 foot
(305 mm) above any door, operable window, or gravity
air inlet into any building. The bottom of the vent terminal shall be located at least 12 inches (305 mm) above
grade.
3. The vent terminal of a direct-vent appliance with an input
of 10,000 Btu per hour (3 kW) or less shall be located at
least 6 inches (152 mm) from any air opening into a
building, and such an appliance with an input over
10,000 Btu per hour (3 kW) but not over 50,000 Btu per
hour (14.7 kW) shall be installed with a 9-inch (230 mm)
vent termination clearance, and an appliance with an input over 50,000 Btu/h (14.7 kw) shall have at least a
12-inch (305 mm) vent termination clearance. The bottom of the vent terminal and the air intake shall be located
at least 12 inches (305 mm) above grade.
4. Through-the-wall vents for Category II and IV appliances and noncategorized condensing appliances shall
not terminate over public walkways or over an area
where condensate or vapor could create a nuisance or
hazard or could be detrimental to the operation of regulators, relief valves, or other equipment. Where local experience indicates that condensate is a problem with
Category I and III appliances, this provision shall also
apply.
503.9 Condensation drainage. Provision shall be made to collect and dispose of condensate from venting systems serving
Category II and IV equipment and noncategorized condensing
appliances in accordance with Section 503.8, Item 4. Where local experience indicates that condensation is a problem, provision shall be made to drain off and dispose of condensate from
venting systems serving Category I and III equipment in accordance with Section 503.8, Item 4.
2003 INTERNATIONAL FUEL GAS CODE®
503.10.2 Materials. Vent connectors shall be constructed in
accordance with Sections 503.10.2.1 through 503.10.2.5.
503.10.2.1 General. A vent connector shall be made of
noncombustible corrosion-resistant material capable of
withstanding the vent gas temperature produced by the
equipment and of sufficient thickness to withstand physical damage.
503.10.2.2 Vent connectors located in unconditioned
areas. Where the vent connector used for equipment
having a draft hood or a Category I appliance is located in
or passes through attics, crawl spaces or other unconditioned spaces, that portion of the vent connector shall be
listed Type B or Type L or listed vent material or listed
material having equivalent insulation properties.
Exception: Single-wall metal pipe located within the
exterior walls of the building in areas having a local
99 percent winter design temperature of 5°F (-15°C)
or higher shall be permitted to be used in unconditioned spaces other than attics and crawl spaces.
503.10.2.3 Residential-type appliance connectors.
Where vent connectors for residential-type appliances
are not installed in attics or other unconditioned spaces,
connectors for listed appliances having draft hoods and
for appliances having draft hoods and equipped with
listed conversion burners shall be one of the following:
1. Type B or Type L vent material;
2. Galvanized sheet steel not less than 0.018 inch
(0.46 mm) thick;
3. Aluminum (1100 or 3003 alloy or equivalent)
sheet not less than 0.027 inch (0.69 mm) thick;
4. Stainless steel sheet not less than 0.012 inch (0.31
mm) thick;
5. Smooth interior wall metal pipe having resistance
to heat and corrosion equal to or greater than that of
Item 2, 3 or 4 above; or
6. A listed vent connector.
Vent connectors shall not be covered with insulation.
Exception: Listed insulated vent connectors shall be
installed according to the terms of their listing.
503.10.2.4 Low-heat equipment. A vent connector for
low-heat equipment shall be a factory-built chimney section or steel pipe having resistance to heat and corrosion
equivalent to that for the appropriate galvanized pipe as
specified in Table 503.10.2.4. Factory-built chimney
sections shall be joined together in accordance with the
chimney manufacturers’ instructions.
81
CHIMNEYS AND VENTS
TABLE 503.10.2.4
MINIMUM THICKNESS FOR GALVANIZED STEEL VENT
CONNECTORS FOR LOW-HEAT APPLIANCES
DIAMETER OF CONNECTOR
(inches)
MINIMUM THICKNESS
(inch)
Less than 6
0.019
0.023
0.029
14 to 16 inclusive
0.034
Over 16
0.056
503.10.3.3 Multiple appliances. Where two or more appliances are connected to a common vent or chimney,
each vent connector shall be sized in accordance with
Section 504 or other approved engineering methods.
1 inch = 25.4 mm.
503.10.2.5 Medium-heat appliances. Vent connectors
for medium-heat equipment and commercial and industrial incinerators shall be constructed of factory-built
medium-heat chimney sections or steel of a thickness not
less than that specified in Table 503.10.2.5 and shall
comply with the following:
1. A steel vent connector for equipment with a vent
gas temperature in excess of 1000°F (538°C),
measured at the entrance to the connector shall be
lined with medium-duty fire brick (ASTM C 64,
Type F), or the equivalent.
2. The lining shall be at least 21/2 inches (64 mm)
thick for a vent connector having a diameter or
greatest cross-sectional dimension of 18 inches
(457 mm) or less.
3. The lining shall be at least 41/2 inches (114 mm)
thick laid on the 41/2-inch (114 mm) bed for a vent
connector having a diameter or greatest cross-sectional dimension greater than 18 inches (457 mm).
4. Factory-built chimney sections, if employed, shall
be joined together in accordance with the chimney
manufacturers’ instructions.
TABLE 503.10.2.5
MINIMUM THICKNESS FOR STEEL VENT CONNECTORS FOR
MEDIUM-HEAT EQUIPMENT AND COMMERCIAL AND
INDUSTRIAL INCINERATORS VENT CONNECTOR SIZE
DIAMETER
(inches)
AREA
(square inches)
MINIMUM THICKNESS
(inch)
Up to 14
Up to 154
0.053
Over 14 to 16
154 to 201
0.067
Over 16 to 18
201 to 254
0.093
Over 18
Larger than 254
For SI:
1 inch = 25.4 mm, 1 square inch = 645.16
0.123
mm2.
503.10.3.4 Common connector/manifold. Where two
or more gas appliances are vented through a common
vent connector or vent manifold, the common vent connector or vent manifold shall be located at the highest
level consistent with available headroom and the required clearance to combustible materials and shall be
sized in accordance with Section 504 or other approved
engineering methods.
As an alternate method applicable only where there
are two draft hood equipped appliances, the effective
area of the common vent connector or vent manifold and
all junction fittings shall be not less than the area of the
larger vent connector plus 50 percent of the area of the
smaller flue collar outlet.
503.10.3.5 Size increase. Where the size of a vent connector is increased to overcome installation limitations
and obtain connector capacity equal to the equipment input, the size increase shall be made at the equipment draft
hood outlet.
503.10.4 Two or more appliances connected to a single
vent. Where two or more vent connectors enter a common
gas vent, chimney flue, or single-wall metal pipe, the
smaller connector shall enter at the highest level consistent
with the available headroom or clearance to combustible
material. Vent connectors serving Category I appliances
shall not be connected to any portion of a mechanical draft
system operating under positive static pressure, such as
those serving Category III or IV appliances.
503.10.3 Size of vent connector. Vent connectors shall be
sized in accordance with Sections 503.10.3.1 through
503.10.3.5.
503.10.5 Clearance. Minimum clearances from vent connectors to combustible material shall be in accordance with
Table 503.7.7.
503.10.3.1 Single draft hood and fan-assisted. A vent
connector for equipment with a single draft hood or for a
Category I fan-assisted combustion system appliance
shall be sized and installed in accordance with Section
504 or other approved engineering methods.
Exception: The clearance between a vent connector and
combustible material shall be permitted to be reduced
where the combustible material is protected as specified
for vent connectors in Table 308.2.
503.10.3.2 Multiple draft hood. For a single appliance
having more than one draft hood outlet or flue collar, the
82
As an alternative method applicable only when all of
the appliances are draft hood equipped, each vent connector shall have an effective area not less than the area of
the draft hood outlet of the appliance to which it is connected.
503.10.6 Flow resistance. A vent connector shall be installed so as to avoid turns or other construction features that
create excessive resistance to flow of vent gases.
2003 INTERNATIONAL FUEL GAS CODE®
á
For SI:
6 to less than 10
10 to 12 inclusive
manifold shall be constructed according to the instructions of the appliance manufacturer. Where there are no
instructions, the manifold shall be designed and constructed in accordance with approved engineering practices. As an alternate method, the effective area of the
manifold shall equal the combined area of the flue collars
or draft hood outlets and the vent connectors shall have a
minimum 1-foot (305 mm) rise.
CHIMNEYS AND VENTS
503.10.7 Joints. Joints between sections of connector piping and connections to flue collars and hood outlets shall be
fastened by one of the following methods:
á
á
1. Sheet metal screws.
2. Vent connectors of listed vent material assembled and
connected to flue collars or draft hood outlets in accordance with the manufacturers’ instructions.
3. Other approved means.
503.10.8 Slope. A vent connector shall be installed without
dips or sags and shall slope upward toward the vent or chimney at least 1/4 inch per foot (21 mm/m).
Exception: Vent connectors attached to a mechanical
draft system installed in accordance with the manufacturers’ instructions.
503.10.9 Length of vent connector. A vent connector shall
be as short as practical and the equipment located as close as
practical to the chimney or vent. Except as provided for in
Section 503.10.3, the maximum horizontal length of a single-wall connector shall be 75 percent of the height of the
chimney or vent. Except as provided for in Section 503.10.3,
the maximum horizontal length of a Type B double-wall
connector shall be 100 percent of the height of the chimney
or vent. For a chimney or vent system serving multiple appliances, the maximum length of an individual connector,
from the appliance outlet to the junction with the common
vent or another connector, shall be 100 percent of the height
of the chimney or vent.
503.10.10 Support. A vent connector shall be supported for
the design and weight of the material employed to maintain
clearances and prevent physical damage and separation of
joints.
503.10.11 Chimney connection. Where entering a flue in a
masonry or metal chimney, the vent connector shall be installed above the extreme bottom to avoid stoppage. Where
a thimble or slip joint is used to facilitate removal of the connector, the connector shall be firmly attached to or inserted
into the thimble or slip joint to prevent the connector from
falling out. Means shall be employed to prevent the connector from entering so far as to restrict the space between its
end and the opposite wall of the chimney flue (see Section
501.9).
503.10.12 Inspection. The entire length of a vent connector
shall be provided with ready access for inspection, cleaning,
and replacement.
503.10.13 Fireplaces. A vent connector shall not be connected to a chimney flue serving a fireplace unless the fireplace flue opening is permanently sealed.
503.10.14 Passage through ceilings, floors, or walls. A
vent connector shall not pass through any ceiling, floor or
fire-resistance-rated wall . A single-wall metal pipe connector shall not pass through any interior wall.
Exception: Vent connectors made of listed Type B or
Type L vent material and serving listed equipment with
draft hoods and other equipment listed for use with Type
B gas vents shall be permitted to pass through walls or
partitions constructed of combustible material if the con2003 INTERNATIONAL FUEL GAS CODE®
nectors are installed with not less than the listed
clearance to combustible material.
503.10.15 Single-wall connector penetrations of combustible walls. A vent connector made of a single-wall
metal pipe shall not pass through a combustible exterior
wall unless guarded at the point of passage by a ventilated
metal thimble not smaller than the following:
1. For listed appliances equipped with draft hoods and
appliances listed for use with Type B gas vents, the
thimble shall be not less than 4 inches (102 mm)
larger in diameter than the vent connector. Where
there is a run of not less than 6 feet (1829 mm) of vent
connector in the open between the draft hood outlet
and the thimble, the thimble shall be permitted to be
not less than 2 inches (51 mm) larger in diameter than
the vent connector.
2. For unlisted appliances having draft hoods, the thimble shall be not less than 6 inches (152 mm) larger in
diameter than the vent connector.
3. For residential and low-heat appliances, the thimble
shall be not less than 12 inches (305 mm) larger in diameter than the vent connector.
Exception: In lieu of thimble protection, all combustible
material in the wall shall be removed from the vent connector a sufficient distance to provide the specified clearance from such vent connector to combustible material.
Any material used to close up such opening shall be
noncombustible.
503.10.16 Medium-heat connectors. Vent connectors for
medium-heat equipment shall not pass through walls or partitions constructed of combustible material.
503.11 Vent connectors for Category II, III, and IV appliances. Vent connectors for Category II, III and IV appliances
shall be as specified for the venting systems in accordance with
Section 503.4.
503.12 Draft hoods and draft controls. The installation of
draft hoods and draft controls shall comply with Sections
503.12.1 through 503.12.7.
503.12.1 Equipment requiring draft hoods. Vented
equipment shall be installed with draft hoods.
Exception: Dual oven-type combination ranges, incinerators, direct-vent equipment, fan-assisted combustion
system appliances, equipment requiring chimney draft
for operation, single firebox boilers equipped with conversion burners with inputs greater than 400,000 Btu per
hour (117 kw), equipment equipped with blast, power, or
pressure burners that are not listed for use with draft
hoods, and equipment designed for forced venting.
503.12.2 Installation. A draft hood supplied with or forming a part of listed vented equipment shall be installed without alteration, exactly as furnished and specified by the
equipment manufacturer.
503.12.2.1 Draft hood required. If a draft hood is not
supplied by the equipment manufacturer where one is required, a draft hood shall be installed, shall be of a listed
or approved type and, in the absence of other instruc83
CHIMNEYS AND VENTS
tions, shall be of the same size as the equipment flue collar. Where a draft hood is required with a conversion
burner, it shall be of a listed or approved type.
503.12.2.2 Special design draft hood. Where it is determined that a draft hood of special design is needed or
preferable for a particular installation, the installation
shall be in accordance with the recommendations of the
equipment manufacturer and shall be approved.
503.12.3 Draft control devices. Where a draft control device is part of the equipment or is supplied by the equipment
manufacturer, it shall be installed in accordance with the
manufacturers’ instructions. In the absence of manufacturers’ instructions, the device shall be attached to the flue collar of the equipment or as near to the equipment as practical.
503.12.4 Additional devices. Equipment (except incinerators) requiring controlled chimney draft shall be permitted
to be equipped with a listed double-acting barometric-draft
regulator installed and adjusted in accordance with the manufacturers’ instructions.
SECTION 504 (IFGS)
SIZING OF CATEGORY I APPLIANCE
VENTING SYSTEMS
504.1 Definitions. The following definitions apply to the tables
in this section.
503.12.5 Location. Draft hoods and barometric draft regulators shall be installed in the same room or enclosure as the
equipment in such a manner as to prevent any difference in
pressure between the hood or regulator and the combustion
air supply.
A P P LI A N C E C ATEG O R I ZED V EN T DIAM ETER/AREA. The minimum vent area/diameter permissible
for Category I appliances to maintain a nonpositive vent static
pressure when tested in accordance with nationally recognized
standards.
503.12.6 Positioning. Draft hoods and draft regulators shall
be installed in the position for which they were designed
with reference to the horizontal and vertical planes and shall
be located so that the relief opening is not obstructed by any
part of the equipment or adjacent construction. The equipment and its draft hood shall be located so that the relief
opening is accessible for checking vent operation.
FAN-ASSISTED COMBUSTION SYSTEM. An appliance
equipped with an integral mechanical means to either draw or
force products of combustion through the combustion chamber
or heat exchanger.
503.12.7 Clearance. A draft hood shall be located so its relief opening is not less than 6 inches (152 mm) from any surface except that of the equipment it serves and the venting
system to which the draft hood is connected. Where a
greater or lesser clearance is indicated on the equipment label, the clearance shall be not less than that specified on the
label. Such clearances shall not be reduced.
503.13 Manually operated dampers. A manually operated
damper shall not be placed in the vent connector for any equipment. Fixed baffles shall not be classified as manually operated
dampers.
503.14 Automatically operated vent dampers. An automatically operated vent damper shall be of a listed type.
503.15 Obstructions. Devices that retard the flow of vent
gases shall not be installed in a vent connector, chimney, or
vent. The following shall not be considered as obstructions:
1. Draft regulators and safety controls specifically listed for
installation in venting systems and installed in accordance with the terms of their listing.
2. Approved draft regulators and safety controls that are designed and installed in accordance with approved engineering methods.
3. Listed heat reclaimers and automatically operated vent
dampers installed in accordance with the terms of their
listing.
84
4. Approved economizers, heat reclaimers, and recuperators installed in venting systems of equipment not required to be equipped with draft hoods, provided that the
gas utilization equipment manufacturer’s instructions
cover the installation of such a device in the venting system and performance in accordance with Sections 503.3
and 503.3.1 is obtained.
5. Vent dampers serving listed appliances installed in accordance with Sections 504.2.1 and 504.3.1 or other approved engineering methods.
FAN Min. The minimum input rating of a Category I fan-assisted appliance attached to a vent or connector.
FAN Max. The maximum input rating of a Category I fan-assisted appliance attached to a vent or connector.
NAT Max. The maximum input rating of a Category I
draft-hood-equipped appliance attached to a vent or connector.
FAN + FAN. The maximum combined appliance input rating
of two or more Category I fan-assisted appliances attached to
the common vent.
FAN + NAT. The maximum combined appliance input rating
of one or more Category I fan-assisted appliances and one or
more Category I draft-hood-equipped appliances attached to
the common vent.
NA. Vent configuration is not allowed due to potential for condensate formation or pressurization of the venting system, or
not applicable due to physical or geometric restraints.
NAT + NAT. The maximum combined appliance input rating
of two or more Category I draft-hood-equipped appliances attached to the common vent.
504.2 Application of single-appliance vent Tables 504.2(1)
through 504.2(5). The application of Tables 504.2(1) through
504.2(5) shall be subject to the requirements of Sections
504.2.1 through 504.2.15.
2003 INTERNATIONAL FUEL GAS CODE®
2003 INTERNATIONAL FUEL GAS CODE®
20
15
10
8
6
61
57
21
25
0
12
23
28
0
12
23
30
0
11
22
29
35
0
10
21
28
34
48
4
6
0
2
5
8
0
2
5
10
0
2
5
10
15
0
2
5
10
15
20
52
58
64
71
75
97
53
59
65
69
94
51
88
49
53
57
84
46
49
51
13
78
Max
2
FAN
0
Min
0
HEIGHT LATERAL
(L)
(H)
(feet)
(feet)
3
35
40
44
48
51
61
37
41
45
48
58
36
40
42
53
35
38
40
50
32
34
36
46
Max
NAT
55
46
38
29
14
0
48
40
30
15
0
41
32
17
0
39
32
16
0
36
30
18
0
Min
FAN
116
124
133
143
149
202
112
121
130
136
191
104
113
118
175
98
103
109
165
91
94
97
152
Max
4
78
84
89
96
100
119
76
82
87
93
112
70
77
81
100
66
71
75
94
61
64
67
86
Max
NAT
69
59
50
38
18
0
61
51
39
20
0
54
41
23
0
51
42
25
0
47
39
27
0
Min
FAN
6
VENT DIAMETER—(D) inches
7
206
217
229
242
250
349
195
206
219
226
327
176
187
194
295
164
171
178
276
149
153
157
251
Max
84
73
62
47
20
0
76
64
49
22
0
67
52
26
0
64
53
28
0
59
50
32
0
Min
FAN
(continued)
134
142
150
160
166
202
128
135
142
150
187
115
124
129
166
109
115
120
155
100
103
105
141
Max
NAT
322
337
351
367
377
540
301
315
330
339
502
267
280
289
447
247
255
263
415
223
227
232
375
Max
206
217
228
241
249
307
198
208
217
225
285
175
188
195
255
165
173
180
235
149
153
157
205
Max
NAT
107
94
81
62
33
0
98
84
64
38
0
88
68
40
0
84
70
42
0
78
66
44
0
Min
FAN
464
481
499
519
531
776
429
445
463
475
716
376
392
402
631
347
356
365
583
310
316
321
524
Max
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
5
TABLE 504.2(1)
TYPE B DOUBLE-WALL GAS VENT
295
308
321
337
346
430
275
288
300
316
390
245
263
273
345
227
237
247
320
205
211
217
285
Max
NAT
125
111
95
73
41
0
115
99
76
45
0
104
81
48
0
99
83
50
0
93
79
53
0
Min
580
600
620
633
970
504
522
533
847
463
473
483
780
413
419
425
698
Max
634
654
675
697
711
1,057
FAN
8
Appliance Vent Connection
Appliance Type
Number of Appliances
410
427
443
460
470
575
373
386
403
414
525
330
346
355
450
303
313
322
415
273
279
285
370
Max
NAT
145
129
112
86
50
0
134
116
90
53
0
122
95
57
0
117
99
60
0
110
93
63
0
Min
530
536
543
897
Max
830
853
877
902
917
1,384
755
777
800
815
1,263
651
671
684
1,096
596
607
619
1,006
FAN
9
537
557
576
599
612
752
491
507
529
544
682
427
446
457
585
396
407
418
537
354
362
370
470
Max
NAT
Connected directly to vent
Category I
Single
CHIMNEYS AND VENTS
85
86
100
50
30
86
82
0
8
20
26
59
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
0
2
5
10
15
20
30
0
2
5
10
15
20
30
50
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
70
76
101
NA
58
64
56
15
70
NA
33
10
77
81
100
Max
30
27
5
FAN
20
9
21
2
0
Min
0
HEIGHT LATERAL
(L)
(H)
(feet)
(feet)
3
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
61
67
NA
NA
NA
50
54
56
64
Max
NAT
NA
NA
47
40
33
26
10
0
69
50
42
35
27
11
0
73
53
44
37
28
13
0
Min
FAN
NA
NA
166
174
182
189
194
218
131
149
158
168
177
183
216
113
132
141
150
160
166
213
Max
4
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
114
119
122
134
NA
90
96
102
108
112
128
Max
NAT
NA
78
59
50
43
33
12
0
84
63
54
45
35
14
0
88
66
57
48
36
14
0
Min
FAN
6
VENT DIAMETER—(D) inches
7
NA
290
311
321
335
347
354
407
250
275
287
299
312
320
397
214
237
249
262
275
283
374
Max
147
92
71
62
53
40
13
0
99
76
66
56
43
15
0
104
80
70
59
45
18
0
Min
FAN
(continued)
NA
NA
NA
NA
NA
NA
NA
NA
NA
169
180
190
200
206
232
NA
154
163
171
176
185
220
Max
NAT
428
483
513
528
542
557
566
665
410
440
455
471
487
497
633
346
374
389
405
421
432
587
Max
NA
NA
344
353
361
369
375
400
259
278
288
298
308
314
363
219
237
249
261
273
280
336
Max
NAT
180
115
90
80
68
52
18
0
123
97
85
73
55
22
0
131
102
90
77
58
27
0
Min
FAN
651
726
763
782
801
820
831
997
605
642
662
681
702
715
932
507
542
560
580
600
613
853
Max
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
5
TABLE 504.2(1)—continued
TYPE B DOUBLE-WALL GAS VENT
405
449
471
482
493
504
510
560
376
401
413
426
438
445
518
321
343
357
371
385
394
475
Max
NAT
197
131
105
93
80
60
21
0
141
113
100
86
65
26
0
149
119
105
91
69
33
0
Min
Max
944
1,029
1,073
1,095
1,118
1,141
1,155
1,411
844
888
911
935
960
975
1,297
702
743
765
788
811
826
1,173
FAN
8
Appliance Vent Connection
Appliance Type
Number of Appliances
575
627
653
666
679
692
700
770
522
556
572
589
605
615
708
444
473
490
507
524
535
650
Max
NAT
217
149
122
109
94
71
25
0
161
131
117
101
77
33
0
171
139
124
107
82
42
0
Min
Max
670
722
747
773
798
813
952
594
628
648
668
688
700
855
Max
NAT
1,288
1,387
1,438
1,465
1,492
1,519
1,536
787
849
880
895
910
926
935
1,908 1,040
1,125
1,176
1,203
1,230
1,259
1,276
1,730
929
977
1,002
1,028
1,055
1,072
1,548
FAN
9
Connected directly to vent
Category I
Single
CHIMNEYS AND VENTS
2003 INTERNATIONAL FUEL GAS CODE®
2003 INTERNATIONAL FUEL GAS CODE®
20
15
10
8
6
0
59
101
130
150
167
2
5
10
15
20
155
15
0
135
2
105
0
63
0
5
142
10
10
68
112
0
0
5
137
8
2
71
0
0
115
128
6
5
110
4
2
0
75
2
1,052
1,078
1,105
1,133
1,150
1,756
953
977
1,003
1,019
1,596
817
839
852
1,377
746
758
770
1,261
661
668
675
1,121
Max
FAN
Min
0
HEIGHT LATERAL
(H)
(L)
(feet)
(feet)
10
665
688
710
738
755
930
610
635
660
675
840
525
547
560
720
490
503
515
660
435
445
455
570
Max
NAT
0
217
195
172
135
81
0
202
177
140
86
0
187
149
93
0
180
154
98
0
171
147
103
720
733
745
970
630
640
650
850
Max
NAT
795
829
850
905
936
967
985
1,578
990
1,609 1,018
1,641 1,045
1,674 1,079
1,694 1,100
2,637 1,350
1,418
1,446
1,476
1,495
2,380 1,240
1,204
1,229
1,244
2,036 1,060
1,097
1,110
1,124
1,858
967
975
982
1,645
Max
FAN
Min
12
0
273
248
220
174
107
0
257
227
182
114
0
238
192
124
0
231
199
130
0
219
191
138
Max
NAT
870
880
890
2,210 1,390
2,245 1,425
2,282 1,460
2,320 1,498
2,343 1,520
3,701 1,900
1,976 1,250
2,009 1,289
2,041 1,327
2,062 1,350
3,323 1,720
1,669 1,080
1,696 1,105
1,713 1,130
2,825 1,450
1,514 1,000
1,528 1,010
1,543 1,020
2,571 1,320
1,330
1,338
1,346
16
18
VENT DIAMETER—(D) inches
335
306
273
219
139
0
318
283
229
147
0
298
243
161
0
289
251
168
0
276
242
178
0
Min
Max
NAT
(continued)
2,948 1,880
2,988 1,910
3,029 1,940
3,071 1,978
3,097 2,000
4,948 2,520
2,623 1,675
2,659 1,712
2,696 1,748
2,719 1,770
4,423 2,270
2,209 1,430
2,238 1,461
2,256 1,480
3,742 1,925
2,000 1,320
2,013 1,330
2,030 1,340
3,399 1,740
1,753 1,150
1,761 1,160
1,769 1,170
2,983 1,530
Max
FAN
404
372
334
270
175
0
385
346
283
186
0
364
300
202
0
354
311
212
0
341
300
225
0
Min
Max
NAT
3,791 2,430
3,835 2,465
3,880 2,500
3,926 2,544
3,955 2,570
6,376 3,250
3,363 2,150
3,402 2,193
3,442 2,235
3,467 2,260
5,678 2,900
2,818 1,840
2,849 1,871
2,868 1,890
4,782 2,450
2,552 1,670
2,563 1,685
2,584 1,700
4,333 2,220
2,235 1,470
2,242 1,475
2,250 1,480
3,802 1,960
Max
FAN
0
495
459
413
337
220
0
479
432
355
239
0
459
382
264
0
450
398
278
0
437
390
296
Max
NAT
4,737 3,050
4,786 3,090
4,835 3,130
4,885 3,174
4,916 3,200
7,988 4,060
4,192 2,700
4,234 2,739
4,278 2,777
4,304 2,800
7,099 3,620
3,504 2,280
3,536 2,318
3,556 2,340
5,955 3,050
3,163 2,070
3,180 2,090
3,196 2,110
5,387 2,750
2,767 1,820
2,774 1,835
2,782 1,850
4,721 2,430
Max
20
0
585
541
489
403
269
0
564
510
426
290
0
546
458
319
0
537
476
336
0
523
469
360
Max
NAT
0
0
0
0
5,792 3,760 689
5,844 3,795 631
5,896 3,830 573
5,950 3,880 475
5,983 3,910 321
9,785 4,980
5,115 3,300 665
5,159 3,343 599
5,204 3,385 501
5,232 3,410 346
8,665 4,410
4,268 2,780 641
4,301 2,818 540
4,322 2,840 378
7,254 3,710
3,850 2,530 630
3,863 2,545 562
3,882 2,560 401
6,555 3,360
3,363 2,210 618
3,370 2,215 555
3,377 2,220 426
0
Min
3,340
3,371
3,390
4,450
3,030
3,040
3,050
4,010
2,650
2,660
2,670
3,520
Max
NAT
3,980
4,019
4,057
4,080
6,953
7,007
7,063
7,119
7,154
4,550
4,575
4,600
4,662
4,700
11,753 6,000
6,129
6,175
6,222
6,251
10,393 5,300
5,099
5,132
5,153
8,682
4,602
4,612
4,634
7,838
4,017
4,023
4,030
6,853
Max
FAN
24
Connected directly to vent
Category I
Single
5,737 2,950
Max
FAN
Min
22
Appliance Vent Connection
FAN
Min
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
2,267 1,170
Max
FAN
Min
14
TABLE 504.2(1)—continued
TYPE B DOUBLE-WALL GAS VENT
Appliance Type
Number of Appliances
CHIMNEYS AND VENTS
87
88
126
141
170
241
15
20
30
50
1,955 1,159
82
108
5
10
1,975 1,170
30
2
876
1,688 1,000
1,802 1,071
1,861 1,107
1,892 1,124
1,923 1,142
2,491 1,310
1,446
924
948
0
1,505
1,536
183
972
996
0
1,567
1,600
1,620 1,010
30
90
5
151
41
2
745
2,231 1,195
1,189
136
0
0
784
807
20
195
30
1,243
1,272
15
160
20
829
851
865
118
143
15
1,301
1,332
1,351
10
125
96
5
10
54
2
1,977 1,060
Max
NAT
292
215
181
163
142
107
44
0
232
195
177
154
118
66
0
246
207
187
164
127
74
0
Min
Max
NAT
2,657 1,550
2,803 1,663
2,880 1,719
2,920 1,747
2,961 1,775
3,002 1,803
3,027 1,820
3,925 2,050
2,214 1,349
2,288 1,408
2,327 1,437
2,366 1,466
2,406 1,495
2,431 1,513
3,441 1,825
1,807 1,130
1,873 1,185
1,908 1,220
1,944 1,254
1,981 1,289
2,004 1,310
3,004 1,550
Max
FAN
12
350
265
226
206
180
136
72
0
287
244
222
196
151
86
0
305
260
237
209
164
98
0
Min
16
18
VENT DIAMETER—(D) inches
Max
NAT
2,786 1,800
3,856 2,250
4,037 2,375
4,133 2,438
4,182 2,469
4,231 2,500
4,282 2,531
4,313 2,550
5,729 2,950
3,150 1,910
3,239 1,987
3,285 2,026
3,332 2,064
3,380 2,102
3,409 2,125
4,934 2,550
2,555 1,585
2,633 1,650
2,674 1,692
2,716 1,733
2,759 1,775
415
319
277
252
223
172
95
0
347
300
274
243
191
113
0
369
319
292
259
206
127
0
Min
Max
NAT
5,289 3,100
5,505 3,267
5,619 3,351
5,678 3,392
5,737 3,434
5,797 3,475
5,834 3,500
7,914 4,050
4,253 2,631
4,356 2,675
4,409 2,721
4,464 2,767
4,520 2,813
4,554 2,840
6,711 3,440
3,433 2,130
3,523 2,200
3,570 2,250
3,617 2,300
3,666 2,350
3,696 2,380
5,725 2,920
Max
FAN
486
378
330
304
268
208
120
0
412
361
330
295
234
141
0
440
384
354
316
252
159
0
Min
Max
NAT
6,956 4,050
7,209 4,279
7,341 4,394
7,409 4,451
7,478 4,509
7,548 4,566
7,591 4,600
10,485 5,300
5,523 3,431
5,641 3,481
5,701 3,534
5,763 3,585
5,826 3,639
5,864 3,670
8,774 4,460
4,442 2,785
4,542 2,870
4,594 2,920
4,647 2,970
4,701 3,020
4,734 3,050
7,420 3,770
Max
FAN
572
446
387
358
318
245
138
0
494
433
396
355
283
171
0
540
467
431
386
312
199
0
Max
NAT
8,841 5,300
9,136 5,509
9,289 5,613
9,367 5,665
9,447 5,717
9,528 5,769
9,577 5,800
13,454 6,700
6,953 4,421
7,086 4,479
7,155 4,511
7,224 4,542
7,295 4,597
7,339 4,630
11,129 5,635
5,574 3,565
5,686 3,650
5,744 3,695
5,803 3,739
5,863 3,783
5,900 3,810
9,341 4,750
Max
20
659
514
452
418
374
293
169
0
577
506
465
419
336
209
0
635
548
507
456
373
241
0
Min
Max
NAT
7,194 4,650
10,979 6,600
11,310 6,850
11,482 6,975
11,569 7,037
11,658 7,100
11,748 7,162
11,803 7,200
16,817 8,600
8,557 5,444
8,704 5,506
8,779 5,546
8,855 5,585
8,933 5,654
8,980 5,695
13,767 6,940
6,842 4,375
6,964 4,480
7,026 4,527
7,090 4,574
7,155 4,622
Max
16,694 8,430
8,239 5,225
8,370 5,310
8,437 5,391
8,505 5,471
8,574 5,552
8,617 5,600
13,848 7,060
Max
NAT
20,578 10,300
752 13,354 8,100
592 13,720 8,391
523 13,910 8,537
487 14,007 8,610
436 14,105 8,683
341 14,204 8,756
204 14,264 8,800
0
672 10,328 6,603
586 10,488 6,670
542 10,570 6,710
491 10,652 6,749
394 10,737 6,818
251 10,788 6,860
0
739
639
590
535
439
285
0
Min
FAN
24
Connected directly to vent
Category I
Single
11,483 5,850
Max
FAN
22
Appliance Vent Connection
FAN
Min
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
4,252 2,170
Max
FAN
14
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
100
50
30
0
Max
FAN
Min
0
HEIGHT LATERAL
(H)
(L)
(feet)
(feet)
10
TABLE 504.2(1)—continued
TYPE B DOUBLE-WALL GAS VENT
Appliance Type
Number of Appliances
CHIMNEYS AND VENTS
2003 INTERNATIONAL FUEL GAS CODE®
2003 INTERNATIONAL FUEL GAS CODE®
20
15
10
8
6
0
2
4
6
0
2
5
8
0
2
5
10
0
2
5
10
15
0
2
5
10
15
20
38
39
NA
NA
37
39
NA
NA
37
39
52
NA
36
38
51
NA
NA
35
37
50
NA
NA
NA
77
51
NA
NA
83
56
NA
NA
87
61
56
NA
93
69
63
NA
NA
96
74
68
NA
NA
NA
HEIGHT LATERAL
FAN
(H)
(L)
(feet)
(feet)
Min Max
3
45
36
33
31
50
39
37
33
53
41
39
34
57
47
44
39
NA
60
50
47
41
NA
NA
Max
NAT
59
60
74
83
58
59
77
90
57
59
76
97
56
57
75
95
NA
54
56
73
93
NA
NA
Max
NAT
Max
FAN
Min
5
Max
NAT
7
VENT DIAMETER—(D) inches
8
Min
Max
FAN
Max
NAT
Min
Max
FAN
Max
NAT
(continued)
211
201
237
263
206
197
245
280
202
193
241
296
195
187
231
284
334
190
182
224
277
325
374
Min
695
423
416
409
777
482
470
458
844
531
518
497
966
631
616
592
568
1,053
708
692
666
640
616
Max
FAN
369
284
277
271
414
321
311
300
449
354
344
325
523
413
400
381
367
573
468
457
437
419
400
Max
267
251
295
327
258
246
305
344
253
242
299
363
244
232
287
349
404
238
227
279
339
393
448
894
541
533
526
1,002
617
604
591
1,093
681
667
643
1,259
812
795
768
742
1,379
914
896
866
838
810
Max
FAN
Min
9
469
368
360
352
536
417
404
392
584
456
443
423
681
543
526
501
484
750
611
596
570
549
526
Max
NAT
371
347
409
449
360
339
418
470
351
332
409
492
336
319
392
470
540
326
309
381
457
526
592
Min
1,118
673
664
656
1,257
768
754
740
1,373
849
834
808
1,591
1,015
997
966
937
1,751
1,146
1,126
1,092
1,060
1,028
Max
10
569
453
443
433
658
513
500
486
718
559
544
520
838
673
657
628
601
927
754
734
702
677
651
Max
NAT
537
498
584
638
521
486
598
665
507
475
584
688
488
457
562
664
750
473
443
547
646
730
808
Max
NAT
1,639 849
979 648
971 638
962 627
1,852 967
1,120 743
1,104 730
1,089 715
2,031 1,057
1,242 848
1,224 825
1,194 788
2,374 1,237
1,491 983
1,469 963
1,433 928
1,399 894
2,631 1,346
1,689 1,098
1,665 1,074
1,626 1,037
1,587 1,005
1,550 973
Max
FAN
Min
12
Single-wall metal connector
Category I
Single
FAN
Appliance Vent Connection
NAT
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
6
151 85 85 249 140 126 373 204 165 522 284
96 66 85 156 104 123 231 156 159 320 213
92 63 102 152 102 146 225 152 187 313 208
89 60 114 147 99 163 220 148 207 307 203
164 93 83 273 154 123 412 234 161 580 319
108 75 83 176 119 121 261 179 155 363 246
102 69 107 168 114 151 252 171 193 352 235
95 64 122 161 107 175 243 163 223 342 225
174 99 82 293 165 120 444 254 158 628 344
117 80 82 193 128 119 287 194 153 400 272
111 76 105 185 122 148 277 186 190 388 261
100 68 132 171 112 188 261 171 237 369 241
190 111 80 325 186 116 499 283 153 713 388
136 93 80 225 149 115 337 224 148 473 314
128 86 102 216 140 144 326 217 182 459 298
116 79 128 201 131 182 308 203 228 438 284
NA 72 158 186 124 220 290 192 272 418 269
200 118 78 346 201 114 537 306 149 772 428
148 99 78 248 165 113 375 248 144 528 344
140 94 100 239 158 141 363 239 178 514 334
129 86 125 223 146 177 344 224 222 491 316
NA 80 155 208 136 216 325 210 264 469 301
NA NA 186 192 126 254 306 196 309 448 285
Max
FAN
Min
4
TABLE 504.2(2)
TYPE B DOUBLE-WALL GAS VENT
Appliance Type
Number of Appliances
CHIMNEYS AND VENTS
89
90
34
37
49
NA
NA
NA
NA
33
36
48
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
99
80
74
NA
NA
NA
NA
99
84
80
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
63
56
52
NA
NA
NA
NA
66
61
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Max
NAT
53
55
72
91
115
NA
NA
51
53
70
89
112
NA
NA
49
51
67
85
132
NA
NA
NA
211
164
157
144
131
NA
NA
213
181
174
160
148
NA
NA
214
192
186
175
162
NA
NA
NA
Max
FAN
Min
4
127
111
106
98
NA
NA
NA
133
121
117
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Max
NAT
76
76
98
122
151
181
NA
73
73
94
118
145
176
NA
69
70
90
113
138
168
231
NA
372
281
271
255
239
223
NA
394
318
308
292
275
257
NA
403
351
342
324
310
295
264
NA
Max
FAN
Min
5
219
183
173
168
157
NA
NA
230
205
198
186
174
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Max
NAT
6
7
VENT DIAMETER—(D) inches
8
110
109
136
171
208
246
NA
105
104
131
162
199
236
315
100
98
125
153
188
224
301
NA
Min
584
429
417
397
377
357
NA
629
495
482
461
441
420
376
659
563
551
532
511
487
448
NA
Max
FAN
334
279
271
257
242
228
NA
361
312
305
292
280
267
NA
395
373
366
354
343
NA
NA
NA
Max
NAT
144
139
171
213
255
298
389
138
133
164
203
244
285
373
131
125
156
191
230
270
355
540
Min
849
610
595
570
547
524
477
928
712
696
671
646
622
573
991
828
813
789
764
739
685
584
Max
FAN
472
392
382
367
349
333
305
515
443
435
420
405
389
NA
555
508
501
486
473
458
NA
NA
Max
NAT
184
175
215
265
312
360
461
176
168
204
253
299
345
442
166
158
194
238
281
325
418
617
Min
1,168
823
806
777
750
723
670
1,292
971
953
923
894
866
809
1,404
1,152
1,134
1,104
1,075
1,046
988
866
Max
FAN
647
533
521
501
481
461
426
704
613
602
583
562
543
502
765
698
688
672
656
639
NA
NA
Max
NAT
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
100
50
30
0
2
5
10
15
20
30
0
2
5
10
15
20
30
0
2
5
10
15
20
30
50
HEIGHT LATERAL
FAN
(H)
(L)
(feet)
(feet)
Min Max
3
TABLE 504.2(2)—continued
TYPE B DOUBLE-WALL GAS VENT
229
219
269
327
379
433
541
220
209
257
313
363
415
521
207
196
240
293
342
391
491
711
Max
NAT
1,542 852
1,069 698
1,049 684
1,017 662
985 638
955 615
895 574
1,724 948
1,273 811
1,252 795
1,217 765
1,183 736
1,150 708
1,086 649
1,900 1,033
1,532 933
1,511 921
1,477 902
1,443 884
1,410 864
1,343 824
1,205 NA
Max
FAN
Min
9
312
296
366
440
507
570
704
295
280
347
418
481
544
674
273
259
322
389
447
507
631
895
Min
Max
NAT
Max
FAN
Min
12
Max
NAT
1,971 1,056 454 2,996 1,545
1,346 863 424 1,999 1,308
1,324 846 524 1,971 1,283
1,287 821 620 1,927 1,234
1,251 794 702 1,884 1,205
1,216 768 780 1,841 1,166
1,147 720 937 1,759 1,101
2,223 1,189 428 3,432 1,818
1,615 1,007 401 2,426 1,509
1,591 991 496 2,396 1,490
1,551 963 589 2,347 1,455
1,512 934 668 2,299 1,421
1,473 906 741 2,251 1,387
1,399 848 892 2,159 1,318
2,479 1,300 395 3,912 2,042
1,970 1,168 371 3,021 1,817
1,945 1,153 460 2,990 1,796
1,905 1,133 547 2,938 1,763
1,865 1,110 618 2,888 1,730
1,825 1,087 690 2,838 1,696
1,747 1,041 834 2,739 1,627
1,591 NA 1,138 2,547 1,489
Max
10
Single-wall metal connector
Category I
Single
FAN
Appliance Vent Connection
Appliance Type
Number of Appliances
CHIMNEYS AND VENTS
2003 INTERNATIONAL FUEL GAS CODE®
2003 INTERNATIONAL FUEL GAS CODE®
20
15
10
8
6
NA
NA
20
NA
5
15
NA
2
NA
NA
10
NA
NA
5
15
NA
2
10
NA
10
NA
2
NA
NA
8
5
NA
NA
5
NA
2
NA
5
2
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
HEIGHT LATERAL
FAN
(H)
(L)
Min Max
(feet)
(feet)
3
NA
NA
NA
36
38
NA
28
35
35
25
28
31
24
26
29
25
28
Max
NAT
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Max
FAN
Min
4
NA
NA
60
68
74
48
55
62
67
50
57
61
48
52
55
49
52
Max
NAT
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Max
FAN
Min
5
TABLE 504.2(3)
MASONRY CHIMNEY
83
97
107
116
124
89
97
107
114
87
96
103
83
88
93
82
86
Max
NAT
7
8
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Min
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Max
FAN
NA
NA
NA
80
51
NA
NA
NA
53
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
503
522
NA
NA
NA
475
NA
NA
NA
NA
NA
NA
NA
NA
Max
FAN
Min
(continued)
148
159
172
184
201
141
153
164
179
139
148
162
127
134
145
117
130
Max
NAT
206
220
237
254
274
201
216
231
250
191
204
221
175
183
198
165
180
Max
NAT
NA
NA
122
95
61
NA
126
99
64
NA
NA
68
NA
NA
NA
NA
NA
Min
NA
NA
627
658
678
NA
565
594
613
NA
NA
519
NA
NA
NA
NA
NA
Max
FAN
296
314
332
350
375
281
296
313
336
263
277
298
239
247
266
231
247
Max
NAT
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
6
186
165
143
113
73
171
148
118
77
155
124
82
NA
NA
84
NA
NA
9
750
780
811
845
867
698
727
759
779
610
638
655
NA
NA
590
NA
NA
Max
FAN
Min
TYPE B DOUBLE-WALL CONNECTOR DIAMETER—(D) inches
to be used with chimney areas within the size limits at bottom
397
418
440
463
491
375
394
416
441
347
365
388
318
328
350
298
320
Max
NAT
214
191
167
133
87
198
173
139
92
182
146
98
173
149
100
NA
NA
955
987
1,022
1,059
1,083
880
912
946
968
762
791
810
695
711
728
NA
NA
Max
10
513
541
566
597
627
485
567
533
562
444
466
491
410
423
446
376
401
Max
NAT
277
251
221
179
121
259
229
186
127
240
196
136
231
201
139
NA
NA
1,406
1,443
1,482
1,523
1,548
1,280
1,315
1,352
1,376
1,093
1,124
1,144
990
1,007
1,024
NA
NA
Max
FAN
Min
12
807
840
879
933
953
742
777
828
841
668
712
724
623
640
651
561
581
Max
NAT
Type B double-wall connector
Category I
Single
FAN
Min
Appliance Vent Connection
Appliance Type
Number of Appliances
CHIMNEYS AND VENTS
91
92
NA
NA
10
30
NA
5
NA
NA
2
NA
NA
30
20
NA
15
NA
20
NA
10
15
NA
5
49
12
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
41
Max
NAT
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Min
88
19
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Max
FAN
4
NA
NA
NA
NA
NA
92
NA
NA
NA
67
76
82
Max
NAT
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Min
137
28
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Max
FAN
5
NA
NA
127
138
151
161
NA
91
107
115
128
137
Max
NAT
7
8
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Min
198
38
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Max
FAN
NA
185
199
215
230
251
NA
159
171
184
198
216
Max
NAT
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
75
47
Min
269
50
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
561
581
Max
FAN
NA
264
282
304
323
351
188
227
243
263
281
303
Max
NAT
NA
NA
NA
NA
83
51
NA
NA
NA
115
90
57
Min
352
63
NA
NA
NA
NA
819
840
NA
NA
NA
709
741
762
Max
FAN
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
6
327
376
400
424
445
477
288
332
353
373
393
421
Max
NAT
81
1,083 596 116
72
416 249
450 203
476 181
500 158
526 125
558
Max Min
1,106 633
NA
860
893
927
962
985
Max
NAT
NA
445
78
NA
977
468 233
511 190
146 1,010 539 170
165
FAN
Max Min Max
NAT
12
Max
NAT
550
95
792
132
1,196 623 295 1,832 984
1,269 669 246 1,916 1,050
1,307 702 222 1,961 1,099
1,347 733 195 2,006 1,147
1,387 774 155 2,052 1,225
1,413 812 99 2,080 1,243
1,035 555 318 1,560 877
1,103 592 264 1,638 940
1,139 621 239 1,679 981
1,176 648 210 1,721 1,025
1,216 683 169 1,766 1,094
1,240 717 111 1,793 1,112
Max
FAN
10
Type B double-wall connector
Category I
Single
126 1,047 567 147
98
61
NA
176
156
135
106
68
Min
FAN
9
Appliance Vent Connection
TYPE B DOUBLE-WALL CONNECTOR DIAMETER—(D) inches
to be used with chimney areas within the size limits at bottom
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
Maximum Internal
Area of Chimney
(square inches)
Minimum Internal
Area of Chimney
(square inches)
50
30
NA
2
HEIGHT LATERAL
FAN
(H)
(L)
Min Max
(feet)
(feet)
3
TABLE 504.2(3)—continued
MASONRY CHIMNEY
Appliance Type
Number of Appliances
CHIMNEYS AND VENTS
2003 INTERNATIONAL FUEL GAS CODE®
2003 INTERNATIONAL FUEL GAS CODE®
20
15
10
8
6
NA
NA
2
5
NA
NA
15
20
NA
10
NA
NA
5
15
NA
2
NA
NA
10
10
NA
NA
2
5
NA
8
NA
2
NA
NA
5
5
NA
2
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
HEIGHT LATERAL
FAN
(H)
(L)
Min Max
(feet)
(feet)
3
NA
NA
NA
35
38
NA
27
32
35
24
28
31
23
26
29
25
28
Max
NAT
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Max
FAN
Min
4
NA
NA
59
67
73
46
54
61
67
49
56
61
47
51
55
48
52
Max
NAT
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
82
87
93
81
86
Max
NAT
NA
NA
NA
NA
NA
86
95
NA
NA
87
96
NA
NA
NA
NA
80
95
NA
NA
NA 105 NA
NA 115 NA
NA 123 NA
NA
NA
NA 106 NA
Max
NAT
8
NA 237 NA
NA 246 NA
NA 265 NA
NA 230 NA
Max
NAT
Min
NA 317 NA
NA 327 NA
NA 349 382
NA 297 NA
NA 319 NA
Max
FAN
Min
NA 189 NA
NA 203 NA
NA 261 NA
NA 345 547
NA 276 334 635 364 459
NA 220 216 518 297 271 654 387 373
NA 174 NA
NA 182 NA
NA 197 NA
NA 164 NA
Max
NAT
NA 247 NA
Max
FAN
Min
9
NA 198 NA
NA 214 NA
NA 278 452 692 372 606
NA 294 392 722 392 531
NA 230 261 591 312 325 775 414 444
873
907
942
965
758
789
808
NA
NA
725
NA
NA
Max
FAN
10
Min
NA
NA
Max
FAN
560
580
Max
NAT
985
621
481 841 1,272 738
504 749 1,309 774
531 637 1,348 825
560 520 1,373 840
441 771 1,088 665
465 657 1,121 710
490 536 1,142 722
408 747
422 673 1,003 638
445 549 1,021 650
375 NA
400 NA
Max
NAT
12
Single-wall metal connector
Category I
Single
80
(continued)
NA 144 NA
NA 156 NA
NA 170 NA
NA 183
NA 202 NA
NA 217 NA
NA 292 NA
NA 392 663
NA 311 442 773 414 591
944
979
510 911 1,394 800
539 823 1,434 835
NA 235 312 622 330 382 806 437 517 1,016 562 733 1,475 875
NA 252 255 655 348 317 842 461 433 1,055 594 623 1,518 930
NA 200 163 520 273 206 675 374 258 864 490 252 1,079 625 508 1,544 950
NA 138 NA
NA 151 NA
NA 163 NA
NA 178 166 473 249 211 611 335 264 776 440 362
NA 137 NA
NA 147 NA
NA 161 NA
NA 126 NA
NA 133 NA
NA 145 NA
NA 116 NA
Max
NAT
NA 180 NA
Max
FAN
Min
NA 130 NA
Max
FAN
Min
NA 113 NA
NA
NA
7
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
6
Appliance Type
Appliance Vent Connection
TYPE B DOUBLE-WALL CONNECTOR DIAMETER—(D) inches
to be used with chimney areas within the size limits at bottom
NA 102 NA
NA
NA
NA
NA
NA
Max
FAN
Min
5
TABLE 504.2(4)
MASONRY CHIMNEY
Number of Appliances
CHIMNEYS AND VENTS
93
94
NA
NA
NA
NA
NA
NA
NA
NA
20
30
2
5
10
15
20
30
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
41
Max
NAT
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Min
88
19
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Max
FAN
4
48
NA
NA
NA
NA
91
NA
NA
NA
66
75
81
Max
NAT
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Min
137
28
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Max
FAN
5
NA
NA
124
136
149
160
NA
88
105
113
127
136
Max
NAT
7
8
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Min
198
38
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Max
FAN
Min
Max
FAN
Max
NAT
Min
Max
FAN
Max
NAT
Min
Max
FAN
Max
NAT
Min
Max
FAN
10
Max
NAT
Min
Max
FAN
12
Single-wall metal connector
Category I
Single
Max
NAT
NA
180
195
212
228
250
NA
155
168
182
196
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
269
50
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
281
327
NA
NA
NA
NA
408
NA
NA
544 1,055 1,539 865
445 643 1,089 585 883 1,624 932
349 428 884 471 572 1,128 615 798 1,668 975
NA
258
278
301
321
NA
NA
NA
NA
NA
352
63
NA
NA
NA
NA
NA
318
370
395
NA
NA
NA
445
78
NA
NA
NA
458
NA
550
95
NA
792
132
610 1,009 1,805 970
504 616 1,251 660 844 1,898 1,040
533 546 1,294 695 761 1,945 1,090
420 355 1,038 562 447 1,337 728 674 1,994 1,140
442 293 1,078 593 398 1,381 770 571 2,044 1,220
350 191 837 475 238 1,103 631 323 1,408 810 463 2,076 1,240
182
223
240
260 300 703 370 370 920 496 500 1,168 644 708 1,713 1,020
279 245 737 391 306 958 524 417 1,210 680 600 1,760 1,090
215 158 578 302 200 759 420 249 982 556 340 1,237 715 489 1,789 1,110
Max
NAT
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
6
9
Appliance Vent Connection
TYPE B DOUBLE-WALL CONNECTOR DIAMETER—(D) inches
to be used with chimney areas within the size limits at bottom
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
49
NA
15
NA
Maximum
Internal Area of
Chimney
(square inches)
NA
10
NA
12
NA
5
NA
Minimum
Internal Area of
Chimney
(square inches)
50
30
NA
2
HEIGHT LATERAL
FAN
(H)
(L)
Min Max
(feet)
(feet)
3
TABLE 504.2(4)—continued
MASONRY CHIMNEY
Appliance Type
Number of Appliances
CHIMNEYS AND VENTS
2003 INTERNATIONAL FUEL GAS CODE®
CHIMNEYS AND VENTS
Number of Appliances
TABLE 504.2(5)
SINGLE-WALL METAL PIPE OR TYPE B
ASBESTOS CEMENT VENT
Appliance Type
Appliance Vent Connection
Single
Category I
Connected directly to pipe or vent
VENT DIAMETER—(D) inches
HEIGHT
(H )
(feet)
6
8
10
15
20
30
50
LATERAL
(L)
(feet)
3
4
5
6
7
8
10
12
MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
0
39
70
116
170
232
312
500
750
2
31
55
94
141
194
260
415
620
5
28
51
88
128
177
242
390
600
0
42
76
126
185
252
340
542
815
2
32
61
102
154
210
284
451
680
5
29
56
95
141
194
264
430
648
10
24
49
86
131
180
250
406
625
0
45
84
138
202
279
372
606
912
2
35
67
111
168
233
311
505
760
5
32
61
104
153
215
289
480
724
10
27
54
94
143
200
274
455
700
15
NA
46
84
130
186
258
432
666
0
49
91
151
223
312
420
684
1,040
2
39
72
122
186
260
350
570
865
5
35
67
110
170
240
325
540
825
10
30
58
103
158
223
308
514
795
15
NA
50
93
144
207
291
488
760
20
NA
NA
82
132
195
273
466
726
0
53
101
163
252
342
470
770
1,190
2
42
80
136
210
286
392
641
990
5
38
74
123
192
264
364
610
945
10
32
65
115
178
246
345
571
910
15
NA
55
104
163
228
326
550
870
20
NA
NA
91
149
214
306
525
832
0
56
108
183
276
384
529
878
1,370
2
44
84
148
230
320
441
730
1,140
5
NA
78
137
210
296
410
694
1,080
10
NA
68
125
196
274
388
656
1,050
15
NA
NA
113
177
258
366
625
1,000
20
NA
NA
99
163
240
344
596
960
30
NA
NA
NA
NA
192
295
540
890
0
NA
120
210
310
443
590
980
1,550
2
NA
95
171
260
370
492
820
1,290
5
NA
NA
159
234
342
474
780
1,230
10
NA
NA
146
221
318
456
730
1,190
15
NA
NA
NA
200
292
407
705
1,130
20
NA
NA
NA
185
276
384
670
1,080
30
NA
NA
NA
NA
222
330
605
1,010
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
2003 INTERNATIONAL FUEL GAS CODE®
95
CHIMNEYS AND VENTS
504.2.1 Vent obstructions. These venting tables shall not
be used where obstructions, as described in Section 503.15,
are installed in the venting system. The installation of vents
serving listed appliances with vent dampers shall be in accordance with the appliance manufacturer’s instructions or
in accordance with the following:
1. The maximum capacity of the vent system shall be determined using the “NAT Max” column.
2. The minimum capacity shall be determined as if the
appliance were a fan-assisted appliance, using the
“FAN Min” column to determine the minimum capacity of the vent system. Where the corresponding
“FAN Min” is “NA,” the vent configuration shall not
be permitted and an alternative venting configuration
shall be utilized.
504.2.2 Minimum size. Where the vent size determined
from the tables is smaller than the appliance draft hood outlet or flue collar, the smaller size shall be permitted to be
used provided that all of the following requirements are met:
1. The total vent height (H) is at least 10 feet (3048 mm).
2. Vents for appliance draft hood outlets or flue collars
12 inches (305 mm) in diameter or smaller are not reduced more than one table size.
3. Vents for appliance draft hood outlets or flue collars
larger than 12 inches (305 mm) in diameter are not reduced more than two table sizes.
4. The maximum capacity listed in the tables for a
fan-assisted appliance is reduced by 10 percent (0.90
× maximum table capacity).
5. The draft hood outlet is greater than 4 inches (102
mm) in diameter. Do not connect a 3-inch-diameter
(76 mm) vent to a 4-inch-diameter (102 mm) draft
hood outlet. This provision shall not apply to fan-assisted appliances.
504.2.3 Vent offsets. Single-appliance venting configurations with zero (0) lateral lengths in Tables 504.2(1),
504.2(2), and 504.2(5) shall not have elbows in the venting
system. For vent configurations with lateral lengths, the
venting tables include allowance for two 90-degree (1.57
rad) turns. For each elbow up to and including 45 degrees
(0.79 rad), the maximum capacity listed in the venting tables shall be reduced by 5 percent. For each elbow greater
than 45 degrees (0.79 rad) up to and including 90 degrees
(1.57 rad), the maximum capacity listed in the venting tables shall be reduced by 10 percent.
504.2.4 Zero lateral. Zero (0) lateral (L) shall apply only to
a straight vertical vent attached to a top outlet draft hood or
flue collar.
504.2.5 High-altitude installations. Sea-level input ratings
shall be used when determining maximum capacity for high
altitude installation. Actual input (derated for altitude) shall
be used for determining minimum capacity for high altitude
installation.
504.2.6 Multiple input rate appliances. For appliances
with more than one input rate, the minimum vent capacity
(FAN Min) determined from the tables shall be less than the
lowest appliance input rating, and the maximum vent capac96
ity (FAN Max/NAT Max) determined from the tables shall
be greater than the highest appliance rating input.
504.2.7 Liner system sizing. Listed corrugated metallic
chimney liner systems in masonry chimneys shall be sized
by using Table 504.2(1) or 504.2(2) for Type B vents with
the maximum capacity reduced by 20 percent (0.80 × maximum capacity) and the minimum capacity as shown in Table
504.2(1) or 504.2(2). Corrugated metallic liner systems installed with bends or offsets shall have their maximum capacity further reduced in accordance with Section 504.2.3.
The 20-percent reduction for corrugated metallic chimney
liner systems includes an allowance for one long-radius
90-degree (157 rad) turn at the bottom of the liner.
504.2.8 Vent area and diameter. Where the vertical vent
has a larger diameter than the vent connector, the vertical
vent diameter shall be used to determine the minimum vent
capacity, and the connector diameter shall be used to determine the maximum vent capacity. The flow area of the vertical vent shall not exceed seven times the flow area of the
listed appliance categorized vent area, flue collar area, or
draft hood outlet area unless designed in accordance with
approved engineering methods.
504.2.9 Chimney and vent locations. Tables 504.2(1),
504.2(2), 504.2(3), 504.2(4) and 504.2(5) shall be used for
chimneys and vents not exposed to the outdoors below the
roof line. A Type B vent or listed chimney lining system
passing through an unused masonry chimney flue shall not
be considered to be exposed to the outdoors. Table 504.2(3)
in combination with Table 504.3(6) shall be used for
clay-tile-lined exterior masonry chimneys, provided all of
the following are met:
1. Vent connector is Type B double-wall.
2. Vent connector length is limited to 11/2 feet for each
inch (18 mm per mm) of vent connector diameter.
3. The appliance is draft hood equipped.
4. The input rating is less than the maximum capacity
given by Table 504.2(3).
5. For a water heater, the outdoor design temperature is
not less than 5°F (-15°C).
6. For a space-heating appliance, the input rating is
greater than the minimum capacity given by Table
504.3(6).
Where these conditions cannot be met, an alternative
venting design shall be used, such as a listed chimney lining
system.
Exception: The installation of vents serving listed appliances shall be permitted to be in accordance with the appliance manufacturer’s instructions and the terms of the
listing.
504.2.10 Corrugated vent connector size. Corrugated
vent connectors shall be not smaller than the listed appliance
categorized vent diameter, flue collar diameter, or draft
hood outlet diameter.
504.2.11 Vent connector size limitation. Vent connectors
shall not be increased in size more than two sizes greater
2003 INTERNATIONAL FUEL GAS CODE®
CHIMNEYS AND VENTS
than the listed appliance categorized vent diameter, flue collar diameter, or draft hood outlet diameter.
TABLE 504.3.2
MAXIMUM VENT CONNECTOR LENGTH
CONNECTOR DIAMETER
MAXIMUM (inches)
CONNECTOR HORIZONTAL
LENGTH (feet)
3
41/2
4
6
5
71/2
504.2.13 Table interpolation. Interpolation shall be permitted in calculating capacities for vent dimensions that fall
between the table entries (see Example 3, Appendix B).
6
9
7
101/2
8
12
504.2.14 Extrapolation prohibited. Extrapolation beyond
the table entries shall not be permitted.
9
131/2
10
15
12
18
14
21
16
24
18
27
20
30
22
33
24
36
504.2.12 Component commingling. In a single run of vent
or vent connector, different diameters and types of vent and
connector components shall be permitted to be used, provided that all such sizes and types are permitted by the tables.
504.2.15 Engineering calculations. For vent heights less
than 6 feet (1829 mm) and greater than shown in the tables,
engineering methods shall be used to calculate vent capacities.
504.3 Application of multiple appliance vent Tables
504.3(1) through 504.3(8). The application of Tables 504.3(1)
through 504.3(8) shall be subject to the requirements of Sections 504.3.1 through 504.3.26.
504.3.1 Vent obstructions. These venting tables shall not
be used where obstructions, as described in Section 503.15,
are installed in the venting system. The installation of vents
serving listed appliances with vent dampers shall be in accordance with the appliance manufacturer’s instructions or
in accordance with the following:
1. The maximum capacity of the vent connector shall be
determined using the NAT Max column.
2. The maximum capacity of the vertical vent or chimney shall be determined using the FAN+NAT column
when the second appliance is a fan-assisted appliance,
or the NAT+NAT column when the second appliance
is equipped with a draft hood.
3. The minimum capacity shall be determined as if the
appliance were a fan-assisted appliance.
3.1. The minimum capacity of the vent connector
shall be determined using the FAN Min column.
3.2. The FAN+FAN column shall be used where
the second appliance is a fan-assisted appliance, and the FAN+NAT column shall be used
where the second appliance is equipped with a
draft hood, to determine whether the vertical
vent or chimney configuration is not permitted
(NA). Where the vent configuration is NA, the
vent configuration shall not be permitted and
an alternative venting configuration shall be
utilized.
504.3.2 Connector length limit. The vent connector shall
be routed to the vent utilizing the shortest possible route. Except as provided in Section 504.3.3, the maximum vent connector horizontal length shall be 11/2 feet for each inch (457
mm per mm) of connector diameter as shown in Table
504.3.2.
2003 INTERNATIONAL FUEL GAS CODE®
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
504.3.3 Connectors with longer lengths. Connectors with
longer horizontal lengths than those listed in Section
504.3.2 are permitted under the following conditions:
1. The maximum capacity (FAN Max or NAT Max) of
the vent connector shall be reduced 10 percent for
each additional multiple of the length listed above.
For example, the maximum length listed above for a
4-inch (102 mm) connector is 6 feet (1829 mm). With
a connector length greater than 6 feet (1829 mm) but
not exceeding 12 feet (3658 mm), the maximum capacity must be reduced by 10 percent (0.90 × maximum vent connector capacity). With a connector
length greater than 12 feet (3658 mm) but not exceeding 18 feet (5486 mm), the maximum capacity must
be reduced by 20 percent (0.80 × maximum vent capacity).
2. For a connector serving a fan-assisted appliance, the
minimum capacity (FAN Min) of the connector shall
be determined by referring to the corresponding single appliance table. For Type B double-wall connectors, Table 504.2(1) shall be used. For single-wall
connectors, Table 504.2(2) shall be used. The height
(H) and lateral (L) shall be measured according to the
procedures for a single-appliance vent, as if the other
appliances were not present.
504.3.4 Vent connector manifold. Where the vent connectors are combined prior to entering the vertical portion of the
common vent to form a common vent manifold, the size of
the common vent manifold and the common vent shall be
determined by applying a 10-percent reduction (0.90 ×
maximum common vent capacity) to the common vent capacity part of the common vent tables. The length of the
common vent connector manifold (LM) shall not exceed
97
CHIMNEYS AND VENTS
11/2 feet for each inch (457 mm per mm) of common vent
connector manifold diameter (D) (see Figure B-11).
height (H) up to the lowest interconnection (see Figure
B-14).
504.3.5 Common vertical vent offset. Where the common
vertical vent is offset, the maximum capacity of the common
vent shall be reduced in accordance with Section 504.3.6.
The horizontal length of the common vent offset (Lo) shall
not exceed 11/2 feet for each inch (457 mm per mm) of common vent diameter.
504.3.15 Multistory common vent offsets. Where used in
multistory systems, vertical common vents shall be Type B
double wall and shall be installed with a listed vent cap.
504.3.6 Elbows in vents. For each elbow up to and including 45 degrees (0.79 rad) in the common vent, the maximum
common vent capacity listed in the venting tables shall be
reduced by 5 percent. For each elbow greater than 45 degrees (0.79 rad) up to and including 90 degrees (1.57 rad),
the maximum common vent capacity listed in the venting tables shall be reduced by 10 percent.
504.3.7 Elbows in connectors. The vent connector capacities listed in the common vent sizing tables include allowance for two 90-degree (1.57 rad) elbows. For each
additional elbow up to and including 45 degrees (0.79 rad),
the maximum vent connector capacity listed in the venting
tables shall be reduced by 5 percent. For each elbow greater
than 45 degrees (0.79 rad) up to and including 90 degrees
(1.57 rad), the maximum vent connector capacity listed in
the venting tables shall be reduced by 10 percent.
504.3.8 Common vent minimum size. The cross-sectional
area of the common vent shall be equal to or greater than the
cross-sectional area of the largest connector.
504.3.9 Common vent fittings. At the point where tee or
wye fittings connect to a common vent, the opening size of
the fitting shall be equal to the size of the common vent.
Such fittings shall not be prohibited from having reducedsize openings at the point of connection of appliance vent
connectors.
504.3.10 High-altitude installations. Sea-level input ratings shall be used when determining maximum capacity for
high-altitude installation. Actual input (derated for altitude)
shall be used for determining minimum capacity for
high-altitude installation.
504.3.11 Connector rise measurement. Connector rise
(R) for each appliance connector shall be measured from the
draft hood outlet or flue collar to the centerline where the
vent gas streams come together.
504.3.12 Vent height measurement. For multiple units of
equipment all located on one floor, available total height (H)
shall be measured from the highest draft hood outlet or flue
collar up to the level of the outlet of the common vent.
504.3.13 Multistory height measurement. For multistory
installations, available total height (H) for each segment of
the system shall be the vertical distance between the highest
draft hood outlet or flue collar entering that segment and the
centerline of the next higher interconnection tee (see Figure
B-13).
504.3.14 Multistory lowest portion sizing. The size of the
lowest connector and of the vertical vent leading to the lowest interconnection of a multistory system shall be in accordance with Table 504.2(1) or 504.2(2) for available total
98
504.3.16 Multistory common vent offsets. Offsets in multistory common vent systems shall be limited to a single offset in each system, and systems with an offset shall comply
with all of the following:
1. The offset angle shall not exceed 45 degrees (0.79 rad)
from vertical.
2. The horizontal length of the offset shall not exceed
11/2 feet for each inch (457 mm per mm) of common
vent diameter of the segment in which the offset is located.
3. For the segment of the common vertical vent containing the offset, the common vent capacity listed in the
common venting tables shall be reduced by 20 percent
(0.80 × maximum common vent capacity).
4. A multistory common vent shall not be reduced in size
above the offset.
504.3.17 Vertical vent maximum size. Where two or more
appliances are connected to a vertical vent or chimney, the
flow area of the largest section of vertical vent or chimney
shall not exceed seven times the smallest listed appliance
categorized vent areas, flue collar area, or draft hood outlet
area unless designed in accordance with approved engineering methods.
504.3.18 Multiple input rate appliances. For appliances
with more than one input rate, the minimum vent connector
capacity (FAN Min) determined from the tables shall be less
than the lowest appliance input rating, and the maximum
vent connector capacity (FAN Max or NAT Max) determined from the tables shall be greater than the highest appliance input rating.
504.3.19 Liner system sizing. Listed, corrugated metallic
chimney liner systems in masonry chimneys shall be sized
by using Table 504.3(1) or 504.3(2) for Type B vents, with
the maximum capacity reduced by 20 percent (0.80 × maximum capacity) and the minimum capacity as shown in Table
504.3(1) or 504.3(2). Corrugated metallic liner systems installed with bends or offsets shall have their maximum capacity further reduced in accordance with Sections 504.3.5
and 504.3.6. The 20-percent reduction for corrugated metallic chimney liner systems includes an allowance for one
long-radius 90-degree (1.57 rad) turn at the bottom of the
liner.
504.3.20 Chimney and vent location. Tables 504.3(1),
504.3(2), 504.3(3), 504.3(4), and 504.3(5) shall be used for
chimneys and vents not exposed to the outdoors below the
roof line. A Type B vent or listed chimney lining system
passing through an unused masonry chimney flue shall not
be considered to be exposed to the outdoors. Tables 504.3(7)
and 504.3(8) shall be used for clay-tile-lined exterior masonry chimneys, provided all of the following conditions are
met:
1. Vent connector is Type B double-wall.
2003 INTERNATIONAL FUEL GAS CODE®
CHIMNEYS AND VENTS
2. At least one appliance is draft hood equipped.
3. The combined appliance input rating is less than the
maximum capacity given by Table 504.3(7a) for
NAT+NAT or Table 504.3(8a) for FAN+NAT.
4. The input rating of each space-heating appliance is
greater than the minimum input rating given by Table
504.3(7b) for NAT+NAT or Table 504.3(8b) for
FAN+NAT.
5. The vent connector sizing is in accordance with Table
504.3(3).
Where these conditions cannot be met, an alternative venting design shall be used, such as a listed chimney lining system.
Exception: Vents serving listed appliances installed in
accordance with the appliance manufacturer’s instructions and the terms of the listing.
504.3.21 Connector maximum and minimum size. Vent
connectors shall not be increased in size more than two sizes
greater than the listed appliance categorized vent diameter,
flue collar diameter, or draft hood outlet diameter. Vent connectors for draft hood-equipped appliances shall not be
smaller than the draft hood outlet diameter. Where a vent
connector size(s) determined from the tables for a fan-assisted appliance(s) is smaller than the flue collar diameter,
the use of the smaller size(s) shall be permitted provided that
the installation complies with all of the following conditions:
1. Vent connectors for fan-assisted appliance flue collars
12 inches (305 mm) in diameter or smaller are not reduced by more than one table size [e.g., 12 inches to
10 inches (305 mm to 254 mm) is a one-size reduction] and those larger than 12 inches (305 mm) in diameter are not reduced more than two table sizes [e.g.,
24 inches to 20 inches (610 mm to 508 mm) is a
two-size reduction].
2. The fan-assisted appliance(s) is common vented with
a draft-hood-equipped appliances(s).
3. The vent connector has a smooth interior wall.
504.3.22 Component commingling. All combinations of
pipe sizes, single-wall, and double-wall metal pipe shall be
allowed within any connector run(s) or within the common
vent, provided all of the appropriate tables permit all of the
desired sizes and types of pipe, as if they were used for the
entire length of the subject connector or vent. Where single-wall and Type B double-wall metal pipes are used for
vent connectors within the same venting system, the common vent must be sized using Table 504.3(2) or 504.3(4), as
appropriate.
504.3.26 Engineering calculations. For vent heights less
than 6 feet (1829 mm) and greater than shown in the tables,
engineering methods shall be used to calculate vent capacities.
SECTION 505 (IFGC)
DIRECT-VENT, INTEGRAL VENT,
MECHANICAL VENT AND
VENTILATION/EXHAUST HOOD VENTING
505.1 General. The installation of direct-vent and integral vent
appliances shall be in accordance with Section 503. Mechanical venting systems and exhaust hood venting systems shall be
designed and installed in accordance with Section 503.
505.1.1 Commercial cooking appliances vented by exhaust hoods. Where commercial cooking appliances are
vented by means of the Type I or Type II kitchen exhaust
hood system that serves such appliances, the exhaust system
shall be fan powered and the appliances shall be interlocked
with the exhaust hood system to prevent appliance operation
when the exhaust hood system is not operating. Dampers
shall not be installed in the exhaust system.
SECTIOSN 506 (IFGC)
FACTORY-BUILT CHIMNEYS
506.1 Building heating appliances. Factory-built chimneys
for building heating appliances producing flue gases having a
temperature not greater than 1,000°F (538°C), measured at the
entrance to the chimney, shall be listed and labeled in accordance with UL 103 and shall be installed and terminated in accordance with the manufacturer’s installation instructions.
506.2 Support. Where factory-built chimneys are supported
by structural members, such as joists and rafters, such members
shall be designed to support the additional load.
506.3 Medium-heat appliances. Factory-built chimneys for
medium-heat appliances producing flue gases having a temperature above 1,000°F (538°C), measured at the entrance to the
chimney, shall be listed and labeled in accordance with UL 959
and shall be installed and terminated in accordance with the
manufacturer’s installation instructions.
504.3.23 Multiple sizes permitted. Where a table permits
more than one diameter of pipe to be used for a connector or
vent, all the permitted sizes shall be permitted to be used.
504.3.24 Table interpolation. Interpolation shall be permitted in calculating capacities for vent dimensions that fall
between table entries (see Appendix B, Example 3).
504.3.25 Extrapolation prohibited. Extrapolation beyond
the table entries shall not be permitted.
2003 INTERNATIONAL FUEL GAS CODE®
99
CHIMNEYS AND VENTS
Number of Appliances
Appliance Type
TABLE 504.3(1)
TYPE B DOUBLE-WALL VENT
Appliance Vent Connection
Two or more
Category I
Type B double-wall connector
VENT CONNECTOR CAPACITY
TYPE B DOUBLE-WALL VENT AND CONNECTOR DIAMETER—(D) inches
3
VENT CONNECTOR
HEIGHT
RISE
FAN
(H)
(R)
Min Max
(feet)
(feet)
6
8
10
15
20
30
50
100
4
5
6
7
8
9
10
APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU/H
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
1
22
37
26
35
66
46
46
106
72
58
164
104
77
225
142
92
296
185
109
376
237
128
466
289
2
23
41
31
37
75
55
48
121
86
60
183
124
79
253
168
95
333
220
112
424
282
131
526
345
3
24
44
35
38
81
62
49
132
96
62
199
139
82
275
189
97
363
248
114
463
317
134
575
386
1
22
40
27
35
72
48
49
114
76
64
176
109
84
243
148
100
320
194
118
408
248
138
507
303
2
23
44
32
36
80
57
51
128
90
66
195
129
86
269
175
103
356
230
121
454
294
141
564
358
3
24
47
36
37
87
64
53
139
101
67
210
145
88
290
198
105
384
258
123
492
330
143
612
402
1
22
43
28
34
78
50
49
123
78
65
189
113
89
257
154
106
341
200
125
436
257
146
542
314
2
23
47
33
36
86
59
51
136
93
67
206
134
91
282
182
109
374
238
128
479
305
149
596
372
3
24
50
37
37
92
67
52
146
104
69
220
150
94
303
205
111
402
268
131
515
342
152
642
417
1
21
50
30
33
89
53
47
142
83
64
220
120
88
298
163
110
389
214
134
493
273
162
609
333
2
22
53
35
35
96
63
49
153
99
66
235
142
91
320
193
112
419
253
137
532
323
165
658
394
3
24
55
40
36
102
71
51
163
111
68
248
160
93
339
218
115
445
286
140
565
365
167
700
444
1
21
54
31
33
99
56
46
157
87
62
246
125
86
334
171
107
436
224
131
552
285
158
681
347
2
22
57
37
34
105
66
48
167
104
64
259
149
89
354
202
110
463
265
134
587
339
161
725
414
3
23
60
42
35
110
74
50
176
116
66
271
168
91
371
228
113
486
300
137
618
383
164
764
466
1
20
62
33
31
113
59
45
181
93
60
288
134
83
391
182
103
512
238
125
649
305
151
802
372
2
21
64
39
33
118
70
47
190
110
62
299
158
85
408
215
105
535
282
129
679
360
155
840
439
3
22
66
44
34
123
79
48
198
124
64
309
178
88
423
242
108
555
317
132
706
405
158
874
494
1
19
71
36
30
133
64
43
216
101
57
349
145
78
477
197
97
627
257
120
797
330
144
984
403
2
21
73
43
32
137
76
45
223
119
59
358
172
81
490
234
100
645
306
123
820
392
148 1,014 478
3
22
75
48
33
141
86
46
229
134
61
366
194
83
502
263
103
661
343
126
842
441
151 1,043 538
1
18
82
37
28
158
66
40
262
104
53
442
150
73
611
204
91
810
266
112 1,038 341
135 1,285 417
2
19
83
44
30
161
79
42
267
123
55
447
178
75
619
242
94
822
316
115 1,054 405
139 1,306 494
3
20
84
50
31
163
89
44
272
138
57
452
109
78
627
272
97
834
355
118 1,069 455
142 1,327 555
COMMON VENT CAPACITY
TYPE B DOUBLE-WALL COMMON VENT DIAMETER (D)—inches
4
VENT
HEIGHT
(H)
(feet)
5
6
7
8
9
10
COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
6
92
81
65
140
116
103
204
161
147
309
248
200
404
314
260
547
434
335
672
520
410
8
101
90
73
155
129
114
224
178
163
339
275
223
444
348
290
602
480
378
740
577
465
10
110
97
79
169
141
124
243
194
178
367
299
242
477
377
315
649
522
405
800
627
495
15
125
112
91
195
164
144
283
228
206
427
352
280
556
444
365
753
612
465
924
733
565
20
136
123
102
215
183
160
314
255
229
475
394
310
621
499
405
842
688
523
1,035
826
640
30
152
138
118
244
210
185
361
297
266
547
459
360
720
585
470
979
808
605
1,209
975
740
50
167
153
134
279
244
214
421
353
310
641
547
423
854
706
550
1,164
977
705
1,451
1,188
860
100
175
163
NA
311
277
NA
489
421
NA
751
658
479
1,025
873
625
1,408
1,215
800
1,784
1,502
975
(continued)
100
2003 INTERNATIONAL FUEL GAS CODE®
CHIMNEYS AND VENTS
Two or more
Number of Appliances
Category I
Appliance Type
TABLE 504.3(1)—continued
TYPE B DOUBLE-WALL VENT
Type B double-wall connector
Appliance Vent Connection
VENT CONNECTOR CAPACITY
TYPE B DOUBLE-WALL VENT AND DIAMETER—(D) inches
12
VENT CONNECTOR
RISE
HEIGHT
(R)
(H )
(feet)
(feet)
6
8
10
15
20
30
50
100
14
16
18
20
22
24
APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Max
Min
Max
Max
Min
Max
Max
Min
2
174
764
496
223
1,046
653
281
1,371
853
346
4
180
897
616
230
1,231
827
287
1,617 1,081
352
6
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
2
186
822
516
238
1,126
696
298
1,478
910
365
1,920 1,150
NA
4
192
952
644
244
1,307
884
305
1,719 1,150
372
2,211 1,460
471
2,737 1,800
560
3,319 2,180
662
3,957 2,590
6
198
1,050
772
252
1,445 1,072
313
1,902 1,390
380
2,434 1,770
478
3,018 2,180
568
3,665 2,640
669
4,373 3,130
2
196
870
536
249
1,195
730
311
1,570
379
2,049 1,205
NA
4
201
997
664
256
1,371
924
318
1,804 1,205
387
2,332 1,535
486
2,887 1,890
581
3,502 2,280
686
4,175 2,710
6
207
1,095
792
263
1,509 1,118
325
1,989 1,455
395
2,556 1,865
494
3,169 2,290
589
3,849 2,760
694
4,593 3,270
2
214
967
568
272
1,334
336
1,760 1,030
408
2,317 1,305
NA
4
221
1,085
712
279
1,499 1,006
344
1,978 1,320
416
2,579 1,665
523
3,197 2,060
624
3,881 2,490
734
4,631 2,960
6
228
1,181
856
286
1,632 1,222
351
2,157 1,610
424
2,796 2,025
533
3,470 2,510
634
4,216 3,030
743
5,035 3,600
2
223
1,051
596
291
1,443
357
1,911 1,095
430
2,533 1,385
NA
4
230
1,162
748
298
1,597 1,064
365
2,116 1,395
438
2,778 1,765
554
3,447 2,180
661
4,190 2,630
772
5,005 3,130
6
237
1,253
900
307
1,726 1,288
373
2,287 1,695
450
2,984 2,145
567
3,708 2,650
671
4,511 3,190
785
5,392 3,790
2
216
1,217
632
286
1,664
367
2,183 1,190
461
2,891 1,540
NA
4
223
1,316
792
294
1,802 1,160
376
2,366 1,510
474
3,110 1,920
619
3,840 2,365
728
4,861 2,860
847
5,606 3,410
6
231
1,400
952
303
1,920 1,410
384
2,524 1,830
485
3,299 2,340
632
4,080 2,875
741
4,976 3,480
860
5,961 4,150
2
206
1,479
689
273
2,023 1,007
350
2,659 1,315
435
3,548 1,665
NA
4
213
1,561
860
281
2,139 1,291
359
2,814 1,685
447
3,730 2,135
580
4,601 2,633
709
5,569 3,185
851
6,633 3,790
6
221
1,631 1,031
290
2,242 1,575
369
2,951 2,055
461
3,893 2,605
594
4,808 3,208
724
5,826 3,885
867
6,943 4,620
2
192
1,923
712
254
2,644 1,050
326
3,490 1,370
402
4,707 1,740
NA
4
200
1,984
888
263
2,731 1,346
336
3,606 1,760
414
4,842 2,220
523
5,982 2,750
639
7,254 3,330
769
8,650 3,950
6
208
2,035 1,064
272
2,811 1,642
346
3,714 2,150
426
4,968 2,700
539
6,143 3,350
654
7,453 4,070
786
8,892 4,810
790
840
910
Min
Max
Max
Min
Max
Max
Min
Max
Max
1,772 1,080
NA
NA
NA
NA
NA
NA
NA
NA
NA
2,069 1,370
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Max
NAT
Max
955
Max
FAN
Min
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
COMMON VENT CAPACITY
TYPE B DOUBLE-WALL COMMON VENT DIAMETER—(D) inches
12
14
16
18
20
22
24
VENT
HEIGHT
(H )
(feet)
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
6
900
696
588
8
994
773
652
10
1,076
841
15
1,247
986
20
1,405
1,116
916
2,006
1,588
1,290
2,722
2,147
1,690
3,561
2,798
2,140
4,548
3,552
2,640
5,573
4,352
3,120
6,749
5,261
3,800
30
1,658
1,327
1,025
2,373
1,892
1,525
3,220
2,558
1,990
4,197
3,326
2,520
5,303
4,193
3,110
6,539
5,157
3,680
7,940
6,247
4,480
50
2,024
1,640
1,280
2,911
2,347
1,863
3,964
3,183
2,430
5,184
4,149
3,075
6,567
5,240
3,800
8,116
6,458
4,500
9,837
7,813
5,475
100
2,569
2,131
1,670
3,732
3,076
2,450
5,125
4,202
3,200
6,749
5,509
4,050
8,597
6,986
5,000 10,681 8,648
COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
1,284
990
815
1,735
1,336
1,065
2,253
1,732
1,345
2,838
2,180
1,660
3,488
1,423
1,103
912
1,927
1,491
1,190
2,507
1,936
1,510
3,162
2,439
1,860
3,890
2,677
1970
4,206
3,226
2,390
2,998
2,200
4,695
3,616
712
1,542
1,200
995
2,093
1,625
1,300
2,727
2,113
1645
3,444
2,665
2,030
2,680
4,241
3,278
2,400
5,123
3,957
2,920
825
1,794
1,410
1,158
2,440
1,910
1,510
3,184
2,484
1,910
4,026
3,133
2,360
4,971
3,862
2,790
6,016
4,670
3,400
5,920 13,004 10,499 7,200
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
2003 INTERNATIONAL FUEL GAS CODE®
101
CHIMNEYS AND VENTS
Two or more
Number of Appliances
Category I
Appliance Type
TABLE 504.3(2)
TYPE B DOUBLE-WALL VENT
Single-wall metal connector
Appliance Vent Connection
VENT CONNECTOR CAPACITY
SINGLE-WALL METAL VENT CONNECTOR DIAMETER—(D) inches
3
CONNECTOR
VENT
HEIGHT
RISE
(R)
(H)
(feet)
(feet)
6
8
10
15
20
30
50
100
4
5
6
7
8
9
10
APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
1
NA
NA
26
NA
NA
46
NA
NA
71
NA
NA
102
207
223
140
262
293
183
325
373
234
447
463
286
2
NA
NA
31
NA
NA
55
NA
NA
85
168
182
123
215
251
167
271
331
219
334
422
281
458
524
344
3
NA
NA
34
NA
NA
62
121
131
95
175
198
138
222
273
188
279
361
247
344
462
316
468
574
385
1
NA
NA
27
NA
NA
48
NA
NA
75
NA
NA
106
226
240
145
285
316
191
352
403
244
481
502
299
2
NA
NA
32
NA
NA
57
125
126
89
184
193
127
234
266
173
293
353
228
360
450
292
492
560
355
3
NA
NA
35
NA
NA
64
130
138
100
191
208
144
241
287
197
302
381
256
370
489
328
501
609
400
1
NA
NA
28
NA
NA
50
119
121
77
182
186
110
240
253
150
302
335
196
372
429
252
506
534
308
2
NA
NA
33
84
85
59
124
134
91
189
203
132
248
278
183
311
369
235
381
473
302
517
589
368
3
NA
NA
36
89
91
67
129
144
102
197
217
148
257
299
203
320
398
265
391
511
339
528
637
413
1
NA
NA
29
79
87
52
116
138
81
177
214
116
238
291
158
312
380
208
397
482
266
556
596
324
2
NA
NA
34
83
94
62
121
150
97
185
230
138
246
314
189
321
411
248
407
522
317
568
646
387
3
NA
NA
39
87
100
70
127
160
109
193
243
157
255
333
215
331
438
281
418
557
360
579
690
437
1
49
56
30
78
97
54
115
152
84
175
238
120
233
325
165
306
425
217
390
538
276
546
664
336
2
52
59
36
82
103
64
120
163
101
182
252
144
243
346
197
317
453
259
400
574
331
558
709
403
3
55
62
40
87
107
72
125
172
113
190
264
164
252
363
223
326
476
294
412
607
375
570
750
457
1
47
60
31
77
110
57
112
175
89
169
278
129
226
380
175
296
497
230
378
630
294
528
779
358
2
51
62
37
81
115
67
117
185
106
177
290
152
236
397
208
307
521
274
389
662
349
541
819
425
3
54
64
42
85
119
76
122
193
120
185
300
172
244
412
235
316
542
309
400
690
394
555
855
482
1
46
69
34
75
128
60
109
207
96
162
336
137
217
460
188
284
604
245
364
768
314
507
951
384
2
49
71
40
79
132
72
114
215
113
170
345
164
226
473
223
294
623
293
376
793
375
520
983
458
3
52
72
45
83
136
82
119
221
123
178
353
186
235
486
252
304
640
331
387
816
423
535 1,013 518
1
45
79
34
71
150
61
104
249
98
153
424
140
205
585
192
269
774
249
345
993
321
476 1,236 393
2
48
80
41
75
153
73
110
255
115
160
428
167
212
593
228
279
788
299
358 1,011 383
490 1,259 469
3
51
81
46
79
157
85
114
260
129
168
433
190
222
603
256
289
801
339
368 1,027 431
506 1,280 527
COMMON VENT CAPACITY
TYPE B DOUBLE-WALL COMMON VENT DIAMETER— (D) inches
4
5
6
7
8
9
10
VENT
HEIGHT
(H )
(feet)
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
6
NA
78
64
NA
113
99
200
158
144
304
244
196
398
310
257
541
429
332
665
515
407
8
NA
87
71
NA
126
111
218
173
159
331
269
218
436
342
285
592
473
373
730
569
460
COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
10
NA
94
76
163
137
120
237
189
174
357
292
236
467
369
309
638
512
398
787
617
487
15
121
108
88
189
159
140
275
221
200
416
343
274
544
434
357
738
599
456
905
718
553
20
131
118
98
208
177
156
305
247
223
463
383
302
606
487
395
824
673
512
1,013
808
626
30
145
132
113
236
202
180
350
286
257
533
446
349
703
570
459
958
790
593
1,183
952
723
954
689
1,418 1,157
838
780
1,741 1,459
948
50
159
145
128
268
233
208
406
337
296
622
529
410
833
686
535
1,139
100
166
153
NA
297
263
NA
469
398
NA
726
633
464
999
846
606
1,378 1,185
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
102
2003 INTERNATIONAL FUEL GAS CODE®
CHIMNEYS AND VENTS
Number of Appliances
Appliance Type
TABLE 504.3(3)
MASONRY CHIMNEY
Appliance Vent Connection
Two or more
Category I
Type B double-wall connector
VENT CONNECTOR CAPACITY
TYPE B DOUBLE-WALL VENT CONNECTOR DIAMETER—(D) inches
3
VENT CONNECTOR
RISE
HEIGHT
(R)
(H )
(feet)
(feet)
6
8
10
15
20
30
50
100
4
5
6
7
8
9
10
APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
1
24
33
21
39
62
40
52
106
67
65
194
101
87
274
141
104
370
201
124
479
253
145
599
319
2
26
43
28
41
79
52
53
133
85
67
230
124
89
324
173
107
436
232
127
562
300
148
694
378
3
27
49
34
42
92
61
55
155
97
69
262
143
91
369
203
109
491
270
129
633
349
151
795
439
1
24
39
22
39
72
41
55
117
69
71
213
105
94
304
148
113
414
210
134
539
267
156
682
335
2
26
47
29
40
87
53
57
140
86
73
246
127
97
350
179
116
473
240
137
615
311
160
776
394
3
27
52
34
42
97
62
59
159
98
75
269
145
99
383
206
119
517
276
139
672
358
163
848
452
1
24
42
22
38
80
42
55
130
71
74
232
108
101
324
153
120
444
216
142
582
277
165
739
348
2
26
50
29
40
93
54
57
153
87
76
261
129
103
366
184
123
498
247
145
652
321
168
825
407
3
27
55
35
41
105
63
58
170
100
78
284
148
106
397
209
126
540
281
147
705
366
171
893
463
1
24
48
23
38
93
44
54
154
74
72
277
114
100
384
164
125
511
229
153
658
297
184
824
375
2
25
55
31
39
105
55
56
174
89
74
299
134
103
419
192
128
558
260
156
718
339
187
900
432
3
26
59
35
41
115
64
57
189
102
76
319
153
105
448
215
131
597
292
159
760
382
190
960
486
1
24
52
24
37
102
46
53
172
77
71
313
119
98
437
173
123
584
239
150
752
312
180
943
397
2
25
58
31
39
114
56
55
190
91
73
335
138
101
467
199
126
625
270
153
805
354
184 1,011 452
3
26
63
35
40
123
65
57
204
104
75
353
157
104
493
222
129
661
301
156
851
396
187 1,067 505
1
24
54
25
37
111
48
52
192
82
69
357
127
96
504
187
119
680
255
145
883
337
175 1,115 432
2
25
60
32
38
122
58
54
208
95
72
376
145
99
531
209
122
715
287
149
928
378
179 1,171 484
3
26
64
36
40
131
66
56
221
107
74
392
163
101
554
233
125
746
317
152
968
418
182 1,220 535
1
23
51
25
36
116
51
51
209
89
67
405
143
92
582
213
115
798
294
140 1,049 392
168 1,334 506
2
24
59
32
37
127
61
53
225
102
70
421
161
95
604
235
118
827
326
143 1,085 433
172 1,379 558
3
26
64
36
39
135
69
55
237
115
72
435
80
98
624
260
121
854
357
147 1,118 474
176 1,421 611
1
23
46
24
35
108
50
49
208
92
65
428
155
88
640
237
109
907
334
134 1,222 454
161 1,589 596
2
24
53
31
37
120
60
51
224
105
67
444
174
92
660
260
113
933
368
138 1,253 497
165 1,626 651
3
25
59
35
38
130
68
53
237
118
69
458
193
94
679
285
116
956
399
141 1,282 540
169 1,661 705
COMMON VENT CAPACITY
MINIMUM INTERNAL AREA OF MASONRY CHIMNEY FLUE (square inches)
12
19
28
38
50
63
78
113
VENT
COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
HEIGHT
FAN FAN NAT FAN FAN NAT FAN FAN NAT FAN FAN NAT FAN FAN NAT FAN FAN NAT FAN FAN NAT FAN FAN NAT
(H)
(feet) +FAN +NAT +NAT +FAN +NAT +NAT +FAN +NAT +NAT +FAN +NAT +NAT +FAN +NAT +NAT +FAN +NAT +NAT +FAN +NAT +NAT +FAN +NAT +NAT
6
NA
74
25
NA
119
46
NA
178
71
NA
257
103
NA
351
143
NA
458
188
NA
582
246
1,041
853
NA
8
NA
80
28
NA
130
53
NA
193
82
NA
279
119
NA
384
163
NA
501
218
724
636
278
1,144
937
408
10
NA
84
31
NA
138
56
NA
207
90
NA
299
131
NA
409
177
606
538
236
776
686
302
1,226 1,010
454
15
NA
NA
36
NA
152
67
NA
233
106
NA
334
152
523
467
212
682
611
283
874
781
365
1,374 1,156
546
20
NA
NA
41
NA
NA
75
NA
250
122
NA
368
172
565
508
243
742
668
325
955
858
419
1,513 1,286
648
30
NA
NA
NA
NA
NA
NA
NA
270
137
NA
404
198
615
564
278
816
747
381
1,062
969
496
1,702 1,473
749
50
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
620
328
879
831
461
1,165 1,089
606
1,905 1,692
922
100
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
348
NA
NA
499
669
2,053 1,921 1,058
NA
NA
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
2003 INTERNATIONAL FUEL GAS CODE®
103
CHIMNEYS AND VENTS
Number of Appliances
Appliance Type
TABLE 504.3(4)
MASONRY CHIMNEY
Appliance Vent Connection
Two or more
Category I
Single-wall metal connector
VENT CONNECTOR CAPACITY
SINGLE-WALL METAL VENT CONNECTOR DIAMETER (D)—inches
3
4
VENT CONNECTOR
HEIGHT
RISE
FAN
(R)
(H)
Min Max
(feet)
(feet)
6
8
10
15
20
30
50
100
5
6
7
8
9
10
APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU/H
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
1
NA
NA
21
NA
NA
39
NA
NA
66
179
191
100
231
271
140
292
366
200
362
474
252
499
594
316
2
NA
NA
28
NA
NA
52
NA
NA
84
186
227
123
239
321
172
301
432
231
373
557
299
509
696
376
3
NA
NA
34
NA
NA
61
134
153
97
193
258
142
247
365
202
309
491
269
381
634
348
519
793
437
1
NA
NA
21
NA
NA
40
NA
NA
68
195
208
103
250
298
146
313
407
207
387
530
263
529
672
331
2
NA
NA
28
NA
NA
52
137
139
85
202
240
125
258
343
177
323
465
238
397
607
309
540
766
391
3
NA
NA
34
NA
NA
62
143
156
98
210
264
145
266
376
205
332
509
274
407
663
356
551
838
450
1
NA
NA
22
NA
NA
41
130
151
70
202
225
106
267
316
151
333
434
213
410
571
273
558
727
343
2
NA
NA
29
NA
NA
53
136
150
86
210
255
128
276
358
181
343
489
244
420
640
317
569
813
403
3
NA
NA
34
97
102
62
143
166
99
217
277
147
284
389
207
352
530
279
430
694
363
580
880
459
1
NA
NA
23
NA
NA
43
129
151
73
199
271
112
268
376
161
349
502
225
445
646
291
623
808
366
2
NA
NA
30
92
103
54
135
170
88
207
295
132
277
411
189
359
548
256
456
706
334
634
884
424
3
NA
NA
34
96
112
63
141
185
101
215
315
151
286
439
213
368
586
289
466
755
378
646
945
479
1
NA
NA
23
87
99
45
128
167
76
197
303
117
265
425
169
345
569
235
439
734
306
614
921
347
2
NA
NA
30
91
111
55
134
185
90
205
325
136
274
455
195
355
610
266
450
787
348
627
986
443
3
NA
NA
35
96
119
64
140
199
103
213
343
154
282
481
219
365
644
298
461
831
391
639 1,042 496
1
NA
NA
24
86
108
47
126
187
80
193
347
124
259
492
183
338
665
250
430
864
330
600 1,089 421
2
NA
NA
31
91
119
57
132
203
93
201
366
142
269
518
205
348
699
282
442
908
372
613 1,145 473
3
NA
NA
35
95
127
65
138
216
105
209
381
160
277
540
229
358
729
312
452
946
412
626 1,193 524
1
NA
NA
24
85
113
50
124
204
87
188
392
139
252
567
208
328
778
287
417 1,022 383
582 1,302 492
2
NA
NA
31
89
123
60
130
218
100
196
408
158
262
588
230
339
806
320
429 1,058 425
596 1,346 545
3
NA
NA
35
94
131
68
136
231
112
205
422
176
271
607
255
349
831
351
440 1,090 466
610 1,386 597
1
NA
NA
23
84
104
49
122
200
89
182
410
151
243
617
232
315
875
328
402 1,181 444
560 1,537 580
2
NA
NA
30
88
115
59
127
215
102
190
425
169
253
636
254
326
899
361
415 1,210 488
575 1,570 634
3
NA
NA
34
93
124
67
133
228
115
199
438
188
262
654
279
337
921
392
427 1,238 529
589 1,604 687
COMMON VENT CAPACITY
MINIMUM INTERNAL AREA OF MASONRY CHIMNEY FLUE (square inches)
12
VENT
HEIGHT
(H)
(feet)
19
28
38
50
63
78
113
COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN FAN NAT FAN FAN NAT FAN FAN NAT FAN FAN NAT FAN FAN NAT FAN FAN NAT FAN FAN NAT FAN FAN NAT
+FAN +NAT +NAT +FAN +NAT +NAT +FAN +NAT +NAT +FAN +NAT +NAT +FAN +NAT +NAT +FAN +NAT +NAT +FAN +NAT +NAT +FAN +NAT +NAT
6
NA
NA
25
NA
118
45
NA
176
71
NA
255
102
NA
348
142
NA
455
187
NA
579
245
846
NA
8
NA
NA
28
NA
128
52
NA
190
81
NA
276
118
NA
380
162
NA
497
217
NA
633
277 1,136 928
405
10
NA
NA
31
NA
136
56
NA
205
89
NA
295
129
NA
405
175
NA
532
234
171
680
300 1,216 1,000 450
15
NA
NA
36
NA
NA
66
NA
230
105
NA
335
150
NA
400
210
677
602
280
866
772
360 1,359 1,139 540
20
NA
NA
NA
NA
NA
74
NA
247
120
NA
362
170
NA
503
240
765
661
321
947
849
415 1,495 1,264 640
30
NA
NA
NA
NA
NA
NA
NA
NA
135
NA
398
195
NA
558
275
808
739
377 1,052 957
490 1,682 1,447 740
50
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
612
325
NA
821
456 1,152 1,076 600 1,879 1,672 910
100
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
494
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16
104
mm2,
NA
NA
NA
663 2,006 1,885 1,046
1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
2003 INTERNATIONAL FUEL GAS CODE®
CHIMNEYS AND VENTS
Number of Appliances
TABLE 504.3(5)
SINGLE-WALL METAL PIPE OR TYPE ASBESTOS CEMENT VENT
Two or more
Appliance Type
Draft hood-equipped
Appliance Vent Connection
Direct to pipe or vent
VENT CONNECTOR CAPACITY
VENT CONNECTOR DIAMETER—(D) inches
CONNECTOR
RISE
( R)
(feet)
3
1
21
40
68
102
146
205
2
28
53
86
124
178
235
3
34
61
98
147
204
275
1
23
44
77
117
179
240
2
30
56
92
134
194
265
3
35
64
102
155
216
298
1
25
49
84
129
190
270
2
31
58
97
145
211
295
3
36
68
107
164
232
321
TOTAL VENT
HEIGHT
( H)
(feet)
4
5
10
12
6
48
78
111
155
205
320
NA
8
55
89
128
175
234
365
505
10
59
95
136
190
250
395
560
15
71
115
168
228
305
480
690
20
80
129
186
260
340
550
790
30
NA
147
215
300
400
650
940
50
NA
NA
NA
360
490
810
1,190
TOTAL VENT
HEIGHT
( H)
(feet)
6-8
15
30 and up
4
5
6
7
8
MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
COMMON VENT CAPACITY
COMMON VENT DIAMETER—(D) inches
6
7
8
COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
2003 INTERNATIONAL FUEL GAS CODE®
105
CHIMNEYS AND VENTS
Number of Appliances
Appliance Type
TABLE 504.3(6)
EXTERIOR MASONRY CHIMNEY
Appliance Vent Connection
One
NAT
Type B double-wall connector
MINIMUM ALLOWABLE INPUT RATING OF SPACE-HEATING APPLIANCE
IN THOUSANDS OF BTU PER HOUR
VENT HEIGHT
(feet)
Internal area of chimney (square inches)
12
19
78
113
6
0
0
0
0
0
8
0
0
0
0
0
0
0
0
0
0
10
0
0
0
0
0
0
0
0
15
NA
0
0
0
0
0
0
0
20
NA
NA
0
123
190
249
184
0
0
30
NA
50
NA
NA
NA
NA
NA
393
334
0
NA
NA
NA
NA
NA
NA
579
6
0
0
68
116
156
180
212
266
8
0
0
82
127
167
187
214
263
10
0
51
97
141
183
201
225
265
15
NA
NA
NA
NA
233
253
274
305
20
NA
NA
NA
NA
NA
307
330
362
30
NA
NA
NA
NA
NA
419
445
485
50
NA
NA
NA
NA
NA
NA
NA
763
6
NA
NA
NA
NA
NA
215
259
349
352
37°F or Greater
28
38
50
63
Local 99% Winter Design Temperature: 37°F or Greater
27 to 36°F
Local 99% Winter Design Temperature: 27 to 36°F
17 to 26°F
Local 99% Winter Design Temperature: 17 to 26°F
8
NA
NA
NA
NA
197
226
264
10
NA
NA
NA
NA
214
245
278
358
15
NA
NA
NA
NA
NA
296
331
398
20
NA
NA
NA
NA
NA
352
387
457
30
NA
NA
NA
NA
NA
NA
507
581
50
NA
NA
NA
NA
NA
NA
NA
NA
6
NA
NA
NA
NA
NA
NA
NA
416
8
NA
NA
NA
NA
NA
NA
312
423
10
NA
NA
NA
NA
NA
289
331
430
15
NA
NA
NA
NA
NA
NA
393
485
20
NA
NA
NA
NA
NA
NA
450
547
30
NA
NA
NA
NA
NA
NA
NA
682
50
NA
NA
NA
NA
NA
NA
NA
972
484
5 to 16°F
Local 99% Winter Design Temperature: 5 to 16°F
-10 to 4°F
Local 99% Winter Design Temperature: -10 to 4°F
6
NA
NA
NA
NA
NA
NA
NA
8
NA
NA
NA
NA
NA
NA
NA
494
10
NA
NA
NA
NA
NA
NA
NA
513
15
NA
NA
NA
NA
NA
NA
NA
586
20
NA
NA
NA
NA
NA
NA
NA
650
30
NA
NA
NA
NA
NA
NA
NA
805
50
NA
NA
NA
NA
NA
NA
NA
1,003
-11°F or Lower
Local 99% Winter Design Temperature: -11°F or Lower
Not recommended for any vent configurations
Note: See Figure B-19 in Appendix B for a map showing local 99 percent winter design temperatures in the United States.
For SI: °C = [(°F - 32]/1.8, 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
106
2003 INTERNATIONAL FUEL GAS CODE®
CHIMNEYS AND VENTS
Number of
Appliances
Two or more
Appliance
Type
NAT + NAT
TABLE 504.3(7a)
EXTERIOR MASONRY CHIMNEY
Appliance Vent
Connection
Type B
double-wall
connector
Combined Appliance Maximum
Input Rating in Thousands of Btu per Hour
INTERNAL AREA OF CHIMNEY (square inches)
12
19
28
38
50
63
78
6
25
46
71
103
143
188
8
28
53
82
119
163
218
10
31
56
90
131
177
15
NA
67
106
152
20
NA
NA
NA
30
NA
NA
NA
50
NA
NA
100
NA
NA
19
28
38
50
63
78
113
Local 99% Winter Design Temperature: 17 to 26°F
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
264
352
246
NA
10
NA
NA
NA
NA
NA
NA
278
358
278
408
15
NA
NA
NA
NA
NA
NA
331
398
236
302
454
20
NA
NA
NA
NA
NA
NA
387
457
212
283
365
546
30
NA
NA
NA
NA
NA
NA
NA
581
NA
NA
325
419
648
NA
NA
NA
496
749
50
NA
NA
NA
NA
NA
NA
NA
862
NA
NA
NA
NA
NA
922
100
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
28
38
6
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
430
NAT + NAT
15
NA
NA
NA
NA
NA
NA
NA
485
Type B
double-wall
connector
20
NA
NA
NA
NA
NA
NA
NA
547
30
NA
NA
NA
NA
NA
NA
NA
682
50
NA
NA
NA
NA
NA
NA
NA
NA
100
NA
NA
NA
NA
NA
NA
NA
NA
Appliance
Type
Appliance Vent
Connection
63
Local 99% Winter Design Temperature: 5 to 16°F
8
Two or more
50
5 to
16°F
10
Number of
Appliances
4°F or
Lower
78
113
Local 99% Winter Design Temperature: 37°F or Greater
6
0
0
0
0
0
0
0
NA
8
0
0
0
0
0
0
0
0
10
0
0
0
0
0
0
0
0
15
NA
0
0
0
0
0
0
0
20
NA
NA
NA
NA
NA
184
0
0
30
NA
NA
NA
NA
NA
393
334
0
50
NA
NA
NA
NA
NA
NA
NA
579
100
NA
NA
NA
NA
NA
NA
NA
NA
27 to
36°F
12
8
INTERNAL AREA OF CHIMNEY (square inches)
37°F or
Greater
INTERNAL AREA OF CHIMNEY (square inches)
6
Minimum Allowable Input Rating of
Space-Heating Appliance in Thousands of Btu per Hour
19
VENT
HEIGHT
(feet)
113
TABLE 504.3(7b)
EXTERIOR MASONRY CHIMNEY
12
Minimum Allowable Input Rating of
Space-Heating Appliance in Thousands of Btu per Hour
17 to
26°F
VENT
HEIGHT
(feet)
VENT
HEIGHT
(feet)
TABLE 504.3(7b)
EXTERIOR MASONRY CHIMNEY—continued
Local 99% Winter Design Temperature: 4°F or Lower
Not recommended for any vent configurations
Note: See Figure B-19 in Appendix B for a map showing local 99 percent
winter design temperatures in the United States.
For SI: °C = [(°F - 32]/1.8, 1 inch = 25.4 mm, 1 square inch = 645.16
mm2, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
Local 99% Winter Design Temperature: 27 to 36°F
6
0
0
68
NA
NA
180
212
NA
8
0
0
82
NA
NA
187
214
263
10
0
51
NA
NA
NA
201
225
265
15
NA
NA
NA
NA
NA
253
274
305
20
NA
NA
NA
NA
NA
307
330
362
30
NA
NA
NA
NA
NA
NA
445
485
50
NA
NA
NA
NA
NA
NA
NA
763
100
NA
NA
NA
NA
NA
NA
NA
NA
2003 INTERNATIONAL FUEL GAS CODE®
107
CHIMNEYS AND VENTS
Number of
Appliances
Two or more
Appliance
Type
FAN + NAT
TABLE 504.3(8a)
EXTERIOR MASONRY CHIMNEY
Appliance Vent
Connection
Type B
double-wall
connector
TABLE 504.3(8b)
EXTERIOR MASONRY CHIMNEY—continued
Minimum Allowable Input Rating of
Space-Heating Appliance in Thousands of Btu per Hour
VENT
HEIGHT
(feet)
INTERNAL AREA OF CHIMNEY (square inches)
12
19
17 to
26°F
Combined Appliance Maximum
Input Rating in Thousands of Btu per Hour
VENT
HEIGHT
(feet)
12
19
28
38
50
63
78
6
74
119
178
257
351
458
582
28
38
50
63
78
113
Local 99% Winter Design Temperature: 17 to 26°F
6
0
55
99
141
182
215
259
349
113
8
52
74
111
154
197
226
264
352
853
10
NA
90
125
169
214
245
278
358
NA
NA
167
212
263
296
331
398
INTERNAL AREA OF CHIMNEY (square inches)
8
80
130
193
279
384
501
636
937
15
10
84
138
207
299
409
538
686
1,010
20
NA
NA
212
258
316
352
387
457
30
NA
NA
NA
362
429
470
507
581
15
NA
152
233
334
467
611
781
1,156
20
NA
NA
250
368
508
668
858
1,286
50
NA
NA
NA
NA
NA
723
766
862
1,473
100
NA
NA
NA
NA
NA
NA
NA
1,669
1,089 1,692
5 to
16°F
30
NA
NA
NA
404
564
747
50
NA
NA
NA
NA
NA
831
100
NA
NA
NA
NA
NA
NA
969
NA
1,921
37°F or
Greater
38
10
NA
111
149
198
250
289
331
430
15
NA
NA
193
247
305
346
393
485
NA
293
360
408
450
547
Type B
double-wall
connector
NA
377
450
531
580
682
50
NA
NA
NA
NA
NA
797
853
972
100
NA
NA
NA
NA
NA
NA
NA
1,833
-10 to
4°F
50
63
78
113
0
0
0
0
8
0
0
0
0
0
0
0
0
10
0
0
0
0
0
0
0
0
15
NA
0
0
0
0
0
0
0
20
NA
NA
123
190
249
184
0
0
30
NA
NA
NA
334
398
393
334
0
50
NA
NA
NA
NA
NA
714
707
579
100
NA
NA
NA
NA
NA
NA
NA
1,600
Local 99% Winter Design Temperature: 27 to 36°F
156
180
212
Local 99% Winter Design Temperature: -10 to 4°F
6
NA
NA
145
196
249
296
349
484
8
NA
NA
159
213
269
320
371
494
10
NA
NA
175
231
292
339
397
513
15
NA
NA
NA
283
351
404
457
586
20
NA
NA
NA
333
408
468
528
650
30
NA
NA
NA
NA
NA
603
667
805
50
NA
NA
NA
NA
NA
NA
955
1,003
100
NA
NA
NA
NA
NA
NA
NA
NA
-11°F or
Lower
Local 99% Winter Design Temperature: -11°F or Lower
Not recommended for any vent configurations
Note: See Figure B-19 in Appendix B for a map showing local 99 percent
winter design temperatures in the United States.
For SI: °C = [(°F - 32]/1.8, 1 inch = 25.4 mm, 1 square inch = 645.16
mm2, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
266
8
0
0
82
127
167
187
214
263
10
0
51
97
141
183
210
225
265
15
NA
111
142
183
233
253
274
305
20
NA
NA
187
230
284
307
330
362
30
NA
NA
NA
330
319
419
445
485
50
NA
NA
NA
NA
NA
672
705
763
100
NA
NA
NA
NA
NA
NA
NA
1,554
108
423
NA
0
116
416
312
NA
0
68
301
269
NA
0
0
252
230
NA
0
0
214
182
30
6
6
166
135
20
Local 99% Winter Design Temperature: 37°F or Greater
27 to
36°F
121
94
FAN + NAT
INTERNAL AREA OF CHIMNEY (square inches)
28
78
NA
Appliance
Type
Minimum Allowable Input Rating of
Space-Heating Appliance in Thousands of Btu per Hour
19
NA
8
Two or more
Appliance Vent
Connection
12
6
Number of
Appliances
TABLE 504.3(8b)
EXTERIOR MASONRY CHIMNEY
VENT
HEIGHT
(feet)
Local 99% Winter Design Temperature: 5 to 16°F
2003 INTERNATIONAL FUEL GAS CODE®